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PubMed1993

Compatibility of one Brazilian and two Venezuelan strains of Schistosoma mansoni with various strains of Biomphalaria glabrata.

For evaluation of the degree of genetic heterogeneity in parasite and snail strains, the compatibility between Biomphalaria glabrata and Schistosoma mansoni from different geographical areas was studied. Venezuelan snails from Bárbula, Manuare (areas of schistosome transmission) and Tinaquillo (non-transmission area) and Brazilian BH snails were exposed to infection with miracidia of both the Venezuelan YT and SM strains and the Brazilian BH strain of S. mansoni. Snail-parasite compatibility was evaluated by quantifying the number of snails shedding cercariae during a period of 35 to 60 days post-infection. The best compatibility appeared to be between the Brazilian parasites and the Brazilian or Venezuelan snails. In contrast, the Brazilian snails appeared to be resistant to infection by the Venezuelan parasites tested. Paradoxically, the compatibility between the sympatric pair of Venezuelan parasites and Venezuelan snails appeared to be lower in comparison with the allopatric association of the Brazilian parasite and the Venezuelan snails. The results suggest an important degree of heterogeneity in the snail and parasite isolates studied and yield biological markers for both organisms.

Animals↗
PubMed1978

Ultrastructural changes in the body wall of Schistosoma mansoni during the transformation of the miracidium into the mother sporocyst in the snail host Biomphalaria pfeifferi.

The ultrastructure of the body wall of the free miracidium of Schistosoma mansoni and the changes occurring within 48 h after penetration into the intermediate host Biomphalaria pfeifferi are described. Within 2 h after penetration the ciliated plates are shed into the haemolymph of the snail and phagocytized by amoebocytes. At the same time the narrow ridges between the plates of the free miracidium expand to form the continuous outer layer of the sporocyst. Within 48 h the entire tegumental structure, consisting of a thin outer layer, connected with sunken nucleated areas, develops to its full extent. The observations are compared with those on Fasciola hepatica.

Animals↗
PubMed1985

The effect of Helisoma duryi on the cercarial production of Schistosoma mansoni-infected Biomphalaria alexandrina: evaluation of chemical interferences and direct competition.

The effect of Helisoma duryi or uninfected Biomphalaria alexandrina conditioning of water, as well as the effect of direct competition with these, on the total cercarial production, growth and survival of Schistosoma mansoni-infected B. alexandrina was investigated. The total cercarial production varied considerably between experimental groups. No differences were found between groups maintained in water-conditioned by H. duryi or by uninfected B. alexandrina with regard to the total cercarial production, growth and survival. The cercarial production was correlated with snail size, but showed no differences between the two treatments. Direct competition with H. duryi resulted in reduced cercarial production and growth of infected B. alexandrina as compared with snails in competition with uninfected conspecifics.

Animals↗
PubMed1992

Calcium localization in the shell-forming tissue of the freshwater snail, Biomphalaria glabrata: a comparative study of various methods for localizing calcium.

The routes calcium might take across the mantle to the shell have been investigated with various electron-microscopical techniques in the freshwater snail Biomphalaria glabrata (Planorbidae, Basommatophora). In chemically-fixed tissue, calcium was precipitated with a tannic acid-antimonate technique in predominantly the intercellular spaces of the outer mantle epithelium and the interstitium below it. Some vacuoles of the outer mantle epithelium and one type of mucus cell in the inner mantle epithelium also contained precipitate. The presence of calcium in the precipitates was proved by electron energy loss spectroscopy combined with electron spectroscopic imaging. Incubation with lead acetate and uranyl acetate revealed binding-sites for calcium in the intercellular spaces of the epithelia interstitium and the mucus cells of the inner mantle epithelium. Precipitates were also seen after all incubations in the calcium spherites of the connective tissue. The concentrations of calcium and other elements were analysed in freeze-dried ultrathin sections of cryofixed mantle tissue by means of energy-dispersive X-ray microanalysis. Only in mitochondria of the musculature could high amounts of calcium and phosphorous be detected.

Animals↗
PubMed1980

Agglutinins and hemolysins from Biomphalaria tenagophila snails.

A saline anti-A and incomplete anti-A,B agglutinin were found in spawn extracts of Biomphalaria tenagophila snails. Significance differences after papain and pronase treatments were also found for A1 and A2 subgroups. The hemolysin titers are high, and unspecific.

ABO Blood-Group System↗
PubMed1978

Ultrastructure, histology, and innervation of the mantle edge of the freshwater pulmonate snails Lymnaea stagnalis and Biomphalaria pfeifferi.

The mantle edge of the freshwater pulmonate snails Lymnaea stagnalis and Biomphalaria pfeifferi was investigated with histochemical and ultrastructural methods. The mantle edge gland, which is involved in shell formation, consists of the periostracal groove and the belt. This belt appears to be composed of various regions. In the area of the periostracal groove a number of subepithelial gland cell types occur; these release their products into the groove. Between the groove cells ciliated free nerve endings terminate; the corresponding perikarya occur in the subepidermal connective tissue. Also in the posterior belt region free nerve endings were observed between the epithelial cells; in addition, a particular type of subepithelial gland cell was found in this area. The epithelial cells of this part of the belt have the ultrastructural characteristics of ion and water transporting cells; they are probably involved in calcium deposition and resorption. The possible role of the free nerve endings and of the subepithelial gland cells is discussed.

Animals↗
PubMed2002

Serine protease and phenoloxidase activities in hemocytes of Biomphalaria glabrata snails with varying susceptibility to infection with the parasite Schistosoma mansoni.

The snail Biomphalaria glabrata possesses hemocytes, which are supposed to interact with the larval stages of the human parasite Schistosoma mansoni. We describe trypsin-like serine protease(s) and phenoloxidase activities in lysates from these hemocytes. Both enzymes have activity optima around pH 9.5. The serine protease was inhibited by EDTA, PMSF, antipain and aprotinin, and the phenoloxidase activity by diethydithiocarbamate. By comparison, the serine protease activity in secretions of S. mansoni cercariae also had an alkaline pH optimum around 10.5 and was sensitive to the same inhibitors. In addition, serine protease activities from snails and cercariae had the same molecular mass of 28 kDa. However, the K(m) value of the serine protease(s) and the K(i) values of different inhibitors were generally lower for the snail enzyme than for the cercarial enzyme. The serine protease activity varied among individual snails but activity in hemocyte lysates and hemolymph correlated strongly. There was no detectable difference in the levels of activity between snails which are susceptible or resistant to schistosome infection.

Animals↗
PubMed2002

Gene expression changes in Schistosoma mansoni sporocysts induced by Biomphalaria glabrata embryonic cells.

Biomphalaria glabrataembryonic (Bge) cells have been shown to provide favourable environmental conditions for the development of Schistosoma mansoni sporocysts. We investigated the effect of Bge excretory-secretory products on metabolic activity and gene transcription in S. mansoni mother sporocysts. Using the differential-display technique, we identified several sporocyst transcripts regulated by exposure to Bge soluble components. Research in databases indicated that six of the eight differential products analysed were homologous to sequences already present in databases. Two transcripts appeared of interest for schistosome development since they could be associated with cell division and protein synthesis in developing sporocysts. Their up-regulation following contact with cell products was confirmed by semi-quantitative RT-PCR. The first fragment coded for a part of the chaperonin containing T-complex protein gamma subunit-like protein of S. mansoni (SmTCP 1-C). The second one represented a new S. mansoni expressed sequence tag encoding a protein homologous to various glutaminyl-tRNA synthetases (GlnRS). The full-length sequence of SmGlnRS was cloned from adult schistosomes and its primary sequence was compared to other GlnRS. The overexpression of SmTCP-1 and SmGlnRS could be correlated with the metabolic changes observed in Bge-exposed sporocysts.

Amino Acid Sequence↗
PubMed2002

Parasite-susceptibility phenotypes of F1 Biomphalaria glabrataprogeny derived from interbreeding Schistosoma mansoni-resistant and -susceptible snails.

In an effort to investigate the 'flow' of parasite-resistance genes through laboratory snail populations, we determined the susceptibility of progeny snails from freely interbreeding parasite-susceptible and parasite-resistant parents. Five parental populations of Biomphalaria glabrata were used to generate the progeny snails. Three of them contained different proportions of Schistosoma mansoni-susceptible albino snails (NMRI stock) and S. mansoni-resistant pigmented snails (BS-90), while single stock controls comprised the other two parental populations. F(1) snails from each parental population were exposed to S. mansoni miracidia. Some of the progeny snails were exposed as juveniles, others as adults. According to Hardy-Weinberg principle predictions, the F(1) generation from the three pigmented/albino parental populations displayed higher than expected numbers of pigmented (resistant) snails and lower than expected numbers of albino (susceptible) snails. Among the assumptions of the Hardy-Weinberg principle that were not met within these populations could include non-random mating, unequal fecundity, different hatching and survival rates of different genotypes, or other life-history differences between snail stocks. It is clear, though, that for these two laboratory snail stocks there is no fitness cost attached to genetic resistance to the parasite.

Animals↗
PubMed2003

Transplantation of in vitro-generated Schistosoma mansoni mother sporocysts into Biomphalaria glabrata.

Specific studies on schistosome gene functions require both access to the parasite stages, preferably the larvae, and to complete the life cycle. In the present study, we investigated whether short-term in vitro cultivation of sporocysts and surgical transplantation into snails could be combined to produce cercariae. Miracidia were maintained in vitro in the presence of Biomphalaria glabrata embryonic (Bge) cells or, alternatively, in Bge-cell-conditioned medium. The transformation of miracidia to mother sporocysts was observed in both cases. Two day-old sporocysts were transplanted into the cephalopedal sinus of recipient snails. Transplantation efficiencies varied between 16% and 43%, depending on the culture of the sporocysts in terms of the number of cercariae producing snails. Cercariae recovered from these snails were used to successfully infect hamsters, demonstrating that short term in vitro-generated sporocysts undergo normal cercariogenesis following transplantation. This combination of in vitro cultivation and transplantation may be useful for novel experimental approaches to investigate the genes involved in larval development or host-parasite molecular interactions.

Animals↗
PubMed2003

Silica treatment increases the susceptibility of the Cabo Frio strain of Biomphalaria tenagophila to Schistosoma mansoni infection but does not alter the natural resistance of the Taim strain.

The present work demonstrates that silica treatment represents a suitable in vivo method to evaluate the role of host phagocytic hemocytes in the mechanisms of resistance to parasitic infection. Silica inoculation into Biomphalaria tenagophila snail induced a significant reduction in the circulating hemolymph granulocytes in both strains tested (Taim and Cabo Frio). The granulocyte reduction was accompanied by a significant increase in the number of circulating dead cells. In B. tenagophila Cabo Frio, silica treatment enhanced snail susceptibility to Schistosoma mansoni, shortening the intramolluskan phase of the parasite and increasing the number of sporocysts and cercariae produced. In B. tenagophila Taim, the same treatment did not abrogate natural resistance to S. mansoni reported for this snail strain. These in vivo results demonstrate that macrophage-like granulocytes are involved in the mechanism of S. mansoni sporocyst destruction in Cabo Frio snails and suggest that another, different mechanism may be responsible to the natural resistance of B. tenagophila Taim.

Animals↗
PubMed2003

Angiostrongylus vasorum (Baillet, 1866) Kamensky, 1905: emergence of third-stage larvae from infected Biomphalaria glabrata snails.

Biomphalaria glabrata snails were experimentally infected with Angiostrongylus vasorum first-stage larvae and divided into four groups of 30 snails. To assess the shedding of third-stage larvae (L3), the snails were maintained under different stimuli: group 1 60 W light bulb for 24 h, group 2 37 degrees C water bath for 24 h, group 3 room temperature (23-25 degrees C) for 24 h, Group 4 room temperature (23-25 degrees C) for up to 15 days. After 24 h, a total of 512 A. vasorum L3, alive and active, were released by snails from group 1, while 2,446 L3 were released from group 2 and five L3 from group 3. After 15 days, snails from group 4 released a total of 44 L3. To evaluate the infectivity of A. vasorum L3, two mongrel dogs were successfully infected with L3 released by snails from groups 1 and 2, confirming that the infection of dogs with A. vasorum L3 was possible, independently of ingestion of the mollusk intermediate host. The results shown in these experiments suggest that angiostrongylosis could be directly transmitted to the definitive hosts, with implications for the parasite's life cycle.

Angiostrongylus↗
PubMed2005

Effects of various larval digeneans on the calcium carbonate content of the shells of Helisoma trivolvis, Biomphalaria glabrata, and Physa sp.

The calcium carbonate concentrations in the shells of Helisoma trivolvis and Physa sp. naturally infected with larval trematodes and Biomphalaria glabrata experimentally infected with larval trematodes were analyzed quantitatively. The larval trematode-snail relationships studied were H. trivolvis infected with larval Echinostoma trivolvis and Physa sp. infected with various larval digeneans, and B. glabrata infected with Echinostoma caproni or Schistosoma mansoni. The calcium carbonate concentrations of the shells of infected snails and uninfected cohorts and of the water in which the snails were maintained were determined by ion exchange chromatography. No significant differences in the calcium carbonate concentrations of shells of infected versus uninfected snails were found. The shells of B. glabrata infected with E. caproni contained significantly less calcium carbonate than the shells of uninfected B. glabrata. The hypercalcification hypothesis, i.e., larval trematodes induce an increase in the calcium concentrations in the shells of their snail hosts, was not upheld in any of the snail-larval digenean systems studied herein.

Animals↗
PubMed2006

High-performance thin-layer chromatographic analysis of neutral lipids and phospholipids in Biomphalaria glabrata patently infected with Echinostoma caproni.

This study examined the effects of larval trematode infection on the neutral lipid and phospholipid content of Biomphalaria glabrata patently infected with the daughter rediae of Echinostoma caproni. Uninfected snails were used as matched controls. As determined by qualitative high-performance silica gel thin-layer chromatography (HPTLC), the major neutral lipids present in the whole bodies and digestive gland-gonad complexes in both snail populations were free sterols, free fatty acids, and triacylglycerols, and the major polar lipids were phosphatidylcholine and phosphatidylethanolamine. Quantitative analysis by HPTLC with visible and UV scanning reflectance densitometry showed no significant differences in the concentrations of these lipids in whole bodies of infected snails vs the controls, but the concentration of triacylglycerols in the infected digestive gland-gonad complex was significantly less than that of the uninfected. No qualitative differences in neutral lipids and phospholipids in shell or plasma samples were found between infected vs uninfected snails.

Animals↗
PubMed1997

Chemoattraction and penetration of Echinostoma trivolvis and E. caproni cercariae in the presence of Biomphalaria glabrata, Helisoma trivolvis, and Lymnaea elodes dialysate.

A petri-dish bioassay was used to study the chemoattraction and penetration of the cercariae of Echinostoma trivolvis and E. caproni in the presence of snail dialysates from Helisoma trivolvis (Pennsylvania and Colorado strains). Biomphalaria glabrata, and Lynmaea elodes. Significant chemoattraction was seen with E. trivolvis cercariae in the presence of all snail dialysates released from nonperforated dialysis sacs with a molecular-weight exclusion of 12,000. Under the same conditions, E. caproni was significantly attracted to B. glabrata and H. trivolvis (CO strain) but not to L. elodes or H. trivolvis (PA strain). Dialysis sacs were perforated with needles to allow the release of snail substances of all molecular weights into the bioassay. Cercariae of both species were significantly attracted to all snail dialysates released from perforated sacs. Moreover, cercariae entered these sacs and penetrated the snails, and 24 h later the percentage of cysts per snail species ranged from 70% to 83% for E. trivolvis and from 73% to 93% for E. caproni. Dialysates released from intact sacs were extracted in choloroform-methanol (2:1) to obtain hydrophilic and lipophilic fractions. When these extracts were placed on agar plugs in the bioassay, the lipophilic fraction, but not the hydrophilic fraction, was mainly chemoattractive.

Animals↗
PubMed1997

Schistosoma mansoni: cercarial shedding patterns from a mixed infection of Biomphalaria glabrata with two (early and late) chronobiological variants.

The cercarial emergence rhythms of Schistosoma mansoni were analyzed for mixed infection of the snail Biomphalaria glabrata with two chronobiological strains, one with an early shedding pattern and the other with a late shedding pattern. Under these conditions, each parasite strain kept its own circadian cercarial emergence pattern. When the chronobiological variants were of the same species, no interference between the trematode larvae occurred during the cercarial emergence process. These results confirm that within the host-parasite system the parasite component is directly responsible for the cercarial emergence pattern.

Animals↗
PubMed1999

Effects of snail-conditioned water from Biomphalaria glabrata on hatching of Echinostoma caproni miracidia.

In vitro studies were done on Echinostoma caproni eggs with fully developed miracidia to determine the effects of snail-conditioned water (SCW) from Biomphalaria glabrata on miracidial hatching in the light. Observations were made on miracidial hatching at 4, 8, 12, 16, 20, and 24 h in multiwell chambers in the presence of SCW (experimentals) versus controls in artificial spring water (ASW). The number of hatched eggs was significantly greater (Student's t-test, P<0.05) in SCW at all times as compared with those maintained in ASW. Significantly greater hatching was also obtained when snails were maintained in intact or perforated dialysis sacs in multiwell chambers as compared with sacs without snails. Agar plugs impregnated with SCW or the hydrophilic fraction of SCW that had been extracted in chloroform-methanol (2:1) did not influence significant hatching. However, the lipophilic fraction of the SCW extract caused significant hatching. Substances in SCW significantly increase hatching of E. caproni miracidia, but details on what these compounds are remain obscure.

Animals↗
PubMed1999

Biomphalaria glabrata embryonic cells express a protein with a domain homologous to the lectin domain of mammalian selectins.

We have cloned from Biomphalaria glabrata, the intermediate host of the helminth parasite Schistosoma mansoni, a 36-kDa apparent-molecular-mass molecule (BgSel) that shares sequence identity with selectins of the cell-adhesion-molecule superfamily. BgSel exhibited in its C-terminal part a putative C-type lectin domain similar to the selectin lectin domain. Using antibodies to the recombinant BgSel protein, we demonstrated the presence of BgSel in snail hemocytes as well as in the cell line derived from B. glabrata embryos (Bge). Anti-BgSel antibodies specifically recognized a 79-kDa component in Bge-cell-secreted products that was supposed to represent the native form of BgSel, as was confirmed after glycosidase treatment. Lectins are known to be implicated in recognition mechanisms participating in humoral and cellular immunity in molluscs. The possible role of BgSel in the interaction between sporocysts and Bge cells, particularly in the in vitro model of sporocyst development dependent on Bge cell factors, remains to be determined.

Amino Acid Sequence↗