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At least 199 records · Page 11Linked to original sources
PubMed1991

Identification of a Schistosoma mansoni sporocyst excretory-secretory antioxidant molecule and its effect on superoxide production by Biomphalaria glabrata hemocytes.

Excretory-secretory (E-S) products obtained during in vitro Schistosoma mansoni miracidium-to-sporocyst transformation were found to contain a 108-kDa polypeptide capable of scavenging both exogenously produced and M-line Biomphalaria glabrata hemocyte-derived superoxide (O2-) anions. Separation of crude transformation E-S products using HPLC and ion exchange chromatography resulted in the separation of two isoforms of the 108-kDa molecule. Using an in vitro phagocytosis assay, both isoforms were found to be capable of reducing O2- production by phagocytically stimulated M-line B. glabrata hemocytes without cell loss and without a concomitant reduction in phagocytosis. Although parasite antioxidant molecules appear to play a role in the evasion of host oxidative defense systems in several parasite-vertebrate systems, no previous reports of a parasite antioxidant capability against the potential of oxidative killing by invertebrate defense systems has been reported. In conjunction with the previously confirmed production of O2- by B. glabrata hemocytes and reports of reactive oxygen metabolite production by hemocytes from several molluscan species, these results indicate that reactive forms of oxygen and parasite antioxidant systems may play an important role in the determination of compatibility in the trematode-mollusc relationship.

Animals↗
PubMed1977

The influence of above-optimal constant temperatures on South African Biomphalaria pfeifferi (Krauss) (Mollusca: Planorbidae).

The effects of constant above-optimal temperatures on the hatching, growth, survival, fecundity and development of the ovotestis of Biomphalaria pfeifferi from Komatipoort, South Africa, have been studied and compared with observations reported on B. glabrata. While rates of gametogenesis at 25 degrees C and ambient temperature (mean 22-8 degrees C) were similar, they were slightly accelerated at 27 degreesC. Fecundity and survival at 27 degrees C were considerably reduced and at 29 degrees C hyperthermia was pronounced.

Animals↗
PubMed1980

Schistosoma mansoni control in Cul de Sac Valley, Saint Lucia. I. A two-year focal surveillance-mollusciciding programme for the control of Biomphalaria glabrata.

An area-wide mollusciciding campaign in Cul de Sac valley, St. Lucia reduced incidence of Schistosoma mansoni from 22% to 4.3% between 1970 and 1975. Following this, a two-year focal surveillance-mollusciciding programme was introduced. Sites of potential transmission of S. mansoni were identified and routinely searched for Biomphalaria glabrata. If found, the site was treated with clonitralide 25% emulsifiable concentrate. Two chemotherapy campaigns supplemented the snail control programme. As a result of the combined measures, incidence of the infection dropped from 4.3% to 1.0% and from 2.2% to 0.6% in areas originally of high and low transmission respectively. The cost of protecting the 7,000 population was US $20,362: of these costs, labour absorbed 68%, transport 24%, equipment 4% and molluscicide 4%. The cost per person per year protected was US $1.45 which compares favourably with the $3.24 of the previous scheme. Although effective and relatively cheap, this programme was still dependent on a high standard of supervision for maximum benefit.

Animals↗
PubMed1981

Reduction in transmission of Schistosoma mansoni by a four-year focal mollusciciding programme against Biomphalaria glabrata in Saint Lucia.

The effect of transmission of Schistosoma mansoni of a focal snail control programme was investigated over four years amongst approximately 1250 people living in five communities in the steep-sided Soufriere river valley, St. Lucia, West Indies. Bayer 6076 was applied from constant flow drip cans to 12 stream sections at a target dose of 8 mg/litre clonitralide every four weeks. Only proven and potential transmission sites were treated; marsh habitats, where Biomphalaria glabrata were widespread, were ignored. In the stream snail numbers were reduced by 94% in the first year and by 100% thereafter. Incidence of new S. mansoni infections amongst children fell from 18% in the last year before control to 6% and 9% after three and four years respectively. Amongst children and adults in the four years of control the conversion/reversion ratio declined leading to a lowering of the over-all prevalence from 40% to 22%. Parasitologically the results were similar to those of a previously evaluated area-wide mollusciciding programme. The mean annual cost per person protected was US $2.60. This figure is atypically high because the topography of the area severely limited the population size.

Adolescent↗
PubMed1984

The influence of fluctuating above-optimal temperature regimes on the fecundity of Biomphalaria pfeifferi (Mollusca: Planorbidae).

Biomphalaria pfeifferi of different sizes were subjected to fluctuating temperature regimes incorporating quantities of above-optimal heat ranging from approximately 2 to 75 degree hours greater than 27 degrees C per day. Fecundity over this range was found to be similar from 2 to 45 deg.h. greater than 27 degrees C/day but above this level egg production fell sharply. Histological examination of the gonads of experimental and control snails showed that not only was gametogenesis retarded above 45 deg.h. greater than 27 degrees C/day but also, and perhaps more importantly, development of the gonad was considerably impaired. It is hoped that this kind of information, which is based on field data, will be useful in assessing the likelihood of Schistosoma mansoni transmission becoming established in newly impounded waters in non-endemic areas.

Animals↗
PubMed1985

Biomphalaria glabrata in Haiti.

Biomphalaria glabrata, an intermediate host for Schistosoma mansoni, was first reported in Haiti in 1891 at one location in the Départment du Nord and in 1977 it was reported at several sites in one additional watershed. Our study identifies two additional locations each on a different watershed plus a third possible site. A wide but discontinuous distribution of the snail on the north coast of Haiti is confirmed (no autochthonous infections with S. mansoni have been reported). While there are many possible explanations for this discontinuous distribution, a role for the competitor Thiara granifera in shaping the current distribution of B. glabrata is suggested. The incursion of B. glabrata into Haiti is not recent but at the same time is not expanding.

Animals↗
PubMed1983

The ultrastructure of the amebocyte-producing organ in Biomphalaria glabrata.

The amebocyte-producing organ (APO) in normal and echinostome-sensitized Biomphalaria glabrata was studied at the ultrastructural level. The APO in unexposed snails consists of small clusters of primary ameboblasts resting on the epithelial cells lining the pericardium. The ameboblasts are held in a loose reticulum formed by extensions from smooth muscle and few fibroblastic cells. Secondary ameboblasts and amebocytes constitute further stages of this cell line. Amebocytes, resembling cells in the snail's circulation, appear in the blood sinus coursing through the interior of the APO. Exposure of snails to echinostome miracidia results in significant morphological changes in the organ. Large clusters of primary and and secondary ameboblasts appear, many of these cells undergoing mitosis. Fully activated APOs consist of masses of cells loosely arranged in zones of progressive maturation. Blood cells in activated APOs were significantly larger than those seen in normal APOs.

Animal Population Groups↗
PubMed1984

Isolation, characterization and functional assessment of a hemagglutinin from the plasma of Biomphalaria glabrata, intermediate host of Schistosoma mansoni.

An agglutinin from the plasma of Biomphalaria glabrata, vector of Schistosoma mansoni, has been isolated and partially characterized. Its isolation is a simple two-step process, yielding an essentially pure preparation that can then be manipulated free from other plasma components. It is a large glycoprotein (10(6) daltons), found in four of the five snail strains tested, and possesses affinity for galactose-type sugar residues. Based upon criteria such as molecular weight, carbohydrate and erythrocyte specificity, physical stability and anatomical source, this agglutinin is considered to be distinct from others reported from this mollusc. Involvement of the agglutinin in the host-parasite interaction is discussed.

Animals↗
PubMed1985

Plasma components which mediate cellular defences in the gastropod mollusc Biomphalaria glabrata.

Blood plasmas from certain strains of Biomphalaria glabrata are known to have components which facilitate a hemocyte-effected cytotoxic response against encapsulated Schistosoma mansoni sporocysts. The possible identity of the factor(s) has been investigated. Sporocysts placed in snail plasma rapidly acquire a wide variety of host plasma antigens, at least some of which are displayed on the parasite surface. Plasmas from strains of snail resistant to the parasite agglutinate fixed sporocysts, while plasmas from susceptible strains fail to do so. Fixed sporocysts incubated in plasma bind selectively a subpopulation of plasma antigens; some are bound uniquely in resistant plasma. Another resembles a hemagglutinin from snail plasma. These and other recently acquired data are discussed in light of increasing evidence for defensive roles of multivalent lectins.

Agglutinins↗
PubMed1989

Phagocytosis of yeast by Biomphalaria glabrata: carbohydrate specificity of hemocyte receptors and a plasma opsonin.

In vitro phagocytosis of yeast cells by hemocytes of the mollusc Biomphalaria glabrata can occur in the absence of plasma, but is enhanced by opsonization in plasma from certain snail strains. We have investigated the carbohydrate specificity of the hemocyte-bound receptor for phagocytosis and the free plasma opsonin using two dominant carbohydrate components of the yeast cell wall (laminarin and mannan). Phagocytic uptake in the absence of plasma of both untreated and opsonized yeast is strongly inhibited by laminarin, but is unaffected by mannan. In contrast, laminarin does not interfere with opsonization whereas mannan blocks the process, blocking the binding of a 57 kD plasma component as detected by Western immunoblot. These results suggest that the opsonic lectin in plasma is not simply a free form of the hemocyte-bound receptor for yeast phagocytosis.

Animals↗
PubMedDate not supplied

Carbohydrate-binding plasma proteins from the gastropod Biomphalaria glabrata: strain specificity and the effects of trematode infection.

As lectins are believed to mediate non-self-recognition in molluscs, carbohydrate-binding proteins (CBP) from the circulating plasma of the gastropod Biomphalaria glabrata were harvested by affinity chromatography using six different monosaccharides as ligands. Pools of plasma were derived from B. glabrata of either the M line strain, which is susceptible to infection with the PR1 strain of the digenetic trematode Schistosoma mansoni, or from the 13-16-R1 strain, which is resistant to infection. For each strain, plasma was obtained from control snails and from snails exposed to infection 1 or 8 days previously with S. mansoni or the related digenean, Echinostoma paraensei, which is able to develop in either host strain. For control snails, only minor interstrain differences were noted. In M line snails exposed 8 days previously to either parasite, marked changes in CBP populations were observed. Only E. paraensei infections produced comparable alterations in 13-16-R1 snails. The most conspicuous changes noted were the increased production of 80-120 kDa CBP in both strains, 150-210 kDa in 13-16-R1 snails, and 190-210 kDa in M line snails. The results demonstrate 1) interstrain differences in CBP, particularly following exposure to trematodes; 2) that infection provokes increased production and diversity of CBP that bind with greater affinity to the columns; and 3) that snails of the same strain respond differently to the two parasites used.

Animals↗
PubMedDate not supplied

Characterization of immunoreactive TNF alpha molecules in the gastropod Biomphalaria glabrata.

In recent years, several studies have demonstrated the existence of cytokine-like molecules in invertebrates, therefore suggesting that cytokines may have been conserved throughout evolution. In this study, we investigated the presence of immunoreactive TNF alpha (ir TNF alpha) in the gastropod mollusc Biomphalaria glabrata, the specific intermediate host for the trematode Schistosoma mansoni. Immunocytochemical study indicated the presence of ir TNF alpha in mollusc hemocytes corresponding to a 53-kDa molecule detected by western blot analysis. Using ELISA tests, we demonstrated the presence of substantial amounts of ir TNF alpha in hemolymph, that were significantly decreased during the S. mansoni infection. The possible role of ir TNF alpha in the regulation of mollusc immune functions and in the host-parasite relationship is discussed.

Animals↗
PubMedDate not supplied

Evidence for a family of schistosome glycan-binding lectins in Biomphalaria alexandrina.

A novel family of isolectins that selectively recognize a schistosome-associated fucosyllactose determinant was identified in the hemolymph of Biomphalaria alexandrina, a snail vector of Schistosoma mansoni. Three lectins of this family were purified by serial affinity chromatography on a column of L-fucose and elution with a gradient of 0.1-1 M L-fucose (designated BaSII and BaSIII), followed by a column of D-glucose and elution with 0.3 M D-glucose (designated BaSI). Assessment of the structural characteristics by one- and two-dimensional gels indicated that, inspite of similarities in native molecular weights, the three lectins were tetramers of noncovalently-associated subunits that were of different sizes and pIs in BaSI, and of equal size but distinct pIs in BaSII and BaSIII. Comparisons of two-dimensional gels of the glycosylated and deglycosylated forms were consistent with the presence of an invariant alpha subunit (13.2 kDa, pI 7.2) constituting the three deglycosylated lectins, which associates with other subunits unique to each lectin, namely a beta subunit (10.1 kDa, pI 5.8) in BaSI, an alpha 1 subunit (13.2 kDa, pI 6.8) in BaSII and BaSIII, and an alpha 2 subunit (13.2 kDa, pI 7.0) in BaSIII. Each of these subunits is subjected to differential post-translational N-linked glycosylations, which accounts for the additional heterogeneity expressed by the glycosylated lectins. Based on miracidial glycoprotein binding and inhibition assays, the three lectins exhibited optimum binding at similar pH and temperature, but were distinct in their binding affinities towards the fucose moiety constituting the fucosyllactose target. These observations indicate that an oligomorphic family of recognition molecules may have evolved to regulate the snails' response to schistosomes.

Animals↗
PubMedDate not supplied

Phagocytosis of latex beads by Biomphalaria glabrata hemocytes is modulated in a strain-specific manner by adsorbed plasma components.

Circulating phagocytes of the mollusc Biomphalaria glabrata help determine the fate of invading Schistosoma mansoni larvae. In mediating cytotoxicity against this trematode parasite, phagocytic hemocytes may interact with unidentified plasma components. In this study, positively and negatively charged latex beads were coated with plasma for use in in vitro phagocytosis assays. Hemocytes from S. mansoni-susceptible and -resistant strains of B. glabrata were tested for their ability to internalize beads coated with homologous and heterologous plasma components. Electrophoretic analysis showed that differences in the plasma polypeptides adsorbed to latex beads were charge-related, but no consistent strain-specific differences were detected. Hemocytes from a susceptible strain phagocytosed negatively charged latex pretreated in plasma form a resistant strain of snail at a higher rate than beads treated in plasma from the susceptible strain. Pretreatment of susceptible hemocytes with resistant plasma reduced subsequent phagocytosis of beads coated with resistant plasma, consistent with blocking of receptors on the susceptible hemocytes with resistant strain plasma components. Exogenous lectins detected no differences in the carbohydrates on beads coated with plasma from either snail strain. However, strain differences in endogenous lectins are suggested by differential binding of neoglycoproteins to plasma coated beads. The plasma component(s) responsible for the differential phagocytosis of beads treated in the two plasma strains by hemocytes from the susceptible strain of B. glabrata remain(s) to be identified.

Animals↗
PubMed1984

The adenylate nucleotide pool in the digestive gland-gonad complex of Biomphalaria glabrata infected by Schistosoma mansoni.

The levels of adenylate nucleotides were examined in the digestive gland and ovotestes of Biomphalaria glabrata during cercarial shedding of Schistosoma mansoni, 10 weeks post-infection. In general, parasitization resulted in decreases in the adenylate levels in both tissues, but the results were not statistically significant. Moreover, the energy charge ratio was not significantly altered. The mean energy charge in ovotestes from uninfected and infected individuals was 0.81 and 0.77, respectively, and that in the digestive gland, 0.70 and 0.66, respectively. Extensive variation was observed in energy charge of digestive gland from infected individuals and this was attributed to possible differences in the degree of infection.

Adenine Nucleotides↗
PubMed1986

Stimulation of Schistosoma mansoni miracidia by a 80 kDa glycoprotein from Biomphalaria glabrata.

Soluble extracts of Biomphalaria glabrata stimulate in vitro incorporation of methionine in Schistosoma mansoni miracidia. Evidence is presented that a unique 80 kDa glycoprotein representing less than 0.01% of total snail proteins and uniformly distributed in the snail body, is responsible for the observed stimulation. This protein specifically acts on the miracidia and this observation suggests that this glycoprotein influences snail penetration and development of miracidia. However, the presence of molecules stimulating S. mansoni miracidia was also demonstrated in S. mansoni nonpermissive molluscs.

Animals↗
PubMed1989

Schistosoma mansoni and its intermediate host Biomphalaria glabrata express a common 39 kilodalton acidic protein.

Two Schistosoma mansoni proteins of 43 and 39 kDa (Sm43 and Sm39) were shown to react with rabbit antibodies produced against Biomphalaria glabrata proteins. Two-dimensional gel electrophoresis of miracidial proteins indicated that Sm43 and Sm39 were acidic proteins (pI 4.8 and 4.9 respectively) and were in vitro translated from miracidial messenger RNA in the same molecular forms. Sm43 and Sm39 were expressed by all parasite stages of S. mansoni. Using anti-Sm43 and anti-Sm39 mouse sera, we demonstrated that both parasite proteins were antigenically related and cross-reacted with a unique 39 kDa (pI 4.9) protein from B. glabrata (Bg39). Cross-reactive components were found in fresh water and land snails but not in vertebrate tissues, suggesting that the 39 kDa protein was specific for invertebrates.

Animals↗
PubMed1990

Structural homology of tropomyosins from the human trematode Schistosoma mansoni and its intermediate host Biomphalaria glabrata.

Molecular mimicry has been considered as a possible way for parasites to escape host immune responses. This work concerns the characterization of protein determinants shared by Schistosoma mansoni and its intermediate host Biomphalaria glabrata. Parasite (Sm39) and mollusc (Bg 39) cross-reactive proteins were identified and shown to induce in rabbit and mouse, antibodies specific for invertebrate determinants. Ultrastructural studies demonstrated that antibodies to Sm39 specifically bound to muscular structures of parasite and mollusc. Molecular cloning and sequencing indicated that Bg39 corresponded to a muscular isoform of tropomyosin. The mollusc sequence showed a 51-65% homology with seven different muscular tropomyosins from vertebrate and invertebrate species. The highest score of homology was observed with S. mansoni tropomyosin, suggesting that cross-reactive determinants could be specific for the trematode and its intermediate host. In miracidia, Sm39 epitopes were also shown to be contained in the vesicles present in epidermal ridges and cellular bodies. Such vesicles are involved in the formation of a protective tegument around sporocysts, suggesting a possible role of cross-reactive tropomyosins in miracidia and/or sporocyst-snail interactions.

Amino Acid Sequence↗