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PubMed1996

Purification and characterization of SM 37: a fucosyllactose determinant-bearing glycoprotein probed by a Biomphalaria alexandrina lectin on adult male schistosomes.

Utilizing a Biomphalaria alexandrina-derived lectin (BaSII) of proven specificity to a Schistosoma mansoni-associated fucosyllactose [(Fuc alpha 1-2)Gal beta 1-4 Glc] determinant, a 37-kDa determinant-bearing glycoprotein (Sm 37) was identified selectively on adult male schistosomes. Sm 37 was purified to homogeneity from extracts of adult male worms metabolically radiolabeled with [35S] methionine by BaSII affinity chromatography followed by separation on an HPLC column. Treatments with endoglycosidases, alkaline borohydride, as well as serial lectin affinity chromatography and analysis on 2-dimensional gels indicated that Sm 37 is synthesized as a 33-kDa polypeptide backbone that expresses the fucosyllactose determinant on the outer chain of a single N-linked complex-type glycan unit of either the biantennary or, to a lesser extent, the tri- or tetra-antennary types. The distinct structures of the complex oligosaccharides accounted for the expression of 2 isomorphs of Sm 37. the glycoprotein lacks other conventional high mannose-type or O-linked oligosaccharides and, as deduced from the N-terminal amino acid sequence, the Sm 37 polypeptide may be distinct from other schistosome polypeptides of known sequence. Based on the structural relatedness of the Sm 37-associated fucosyllactose determinant to the antigenic blood group H trisaccharide, these observations may have implications for mechanisms of these host-parasite interactions.

Amino Acid Sequence↗
PubMedDate not supplied

Neotropical planorbid snails with apertural lamellae. I. Biomphalaria helophila (Orbigny, 1835).

A definition of Biomphalaria helophila (Orbigny, 1835) is presented, based on examination of the shell and reproductive system of topotypic specimens and extended to a number of samples from other localities. The following nominal species and subspecies, collected from type localities, proved junior synonyms of B. helophila. Planorbis albicans Pfeiffer, 1839, Planorbis dentatus Gould, 1844; Planorbis dentiferus CB Adams, 1845; Planorbis dentiferus edentatus CB Adams, 1851; Planorbis dentiens Morelet, 1849; Planorbula dentiens edentula Fischer & Crosse, 1880; Planorbis stagnicola Morelet, 1851; and Tropicorbis shimeki FC Baker, 1945. B. helophila was also identified in samples from Costa Rica, Guatemala, Haiti, Dominican Republic, Puerto Rico and Barbados.

Animals↗
PubMed1996

Differences in susceptibility of Biomphalaria alexandrina to Schistosoma mansoni from Gize and Dakahlia Governorates, Egypt.

Biomphalaria alexandrina snails were collected from irrigation canals at Gize and Dakahlia Governorates. They were exposed to strains of Schistosoma mansoni from these localities. The snails showed different rates of susceptibility to the parasite. There was a high range of snail sensitivity to S. mansoni infection (53.9%-60.7%) when snail populations and parasite strains were from the same governorate. Supporting this was the high cercarial production from infected snails of these cases (288.2 cercariae/ snail/week of Dakahlia-Dakahlia group). However, snail populations and parasite strains from different Governorates (Gize-Dakahlia) exhibited poor values of snail sensitivity and cercarial production with significant variations from those of the group of the same governorate.

Animals↗
PubMed1977

Effects of heavy metals (cadmium, copper, chromium and lead) on a freshwater snail: Biomphalaria glabrata Say (Gastropoda, Prosobranchia).

This study concerns the effects of heavy metals (cadmium, copper and chromium) on the mortality and fecundity of the adults of Biomphalaria glabrata and the viability of their embryos. Embryos were also tested for lead. The concentrations used ranged from 0 ppm to 4.0 ppm for Cd2+ and Cu2+ and from 0 to 1.4 ppm for Cr6+. Cadmium and copper were far more toxic than chromium. Fertility was abolished by 0.1 ppm of cadmium and copper and fecundity was severely affected by chromium. Some evident sublethal effects were observed. Survival of the hatchlings treated with chromium was of the same order of magnitude as that of the controls and sexual maturity did not show any delay. Forty-one percent of the embryos kept at concentrations of 0.1 ppm Pb2+ completed their development in 51 days, that is, with a delay of 37 days. The hatchlings at 0.1 ppm died after 15 days. The advantages of using freshwater pulmonates as a toxicity test are discussed.

Animals↗
PubMed1997

[Susceptibility of Biomphalaria tenagophila from the Paraná and Uruguay River basins to Schistosoma mansoni].

To study the possibility that schistosomiasis might be able to spread into the basins of the Paraná and Uruguay rivers, 1,711 snails were experimentally exposed to infection with Schistosoma mansoni. These snails were laboratory-bred progeny of Biomphalaria tenagophila collected from 15 populations in the geographic area under consideration. Three strains of S. mansoni were used: BH2, adapted to B. glabrata, and SJ and SJ2 adapted to B. tenagophila. None of the 543 snails exposed to the BH2 strain became infected, nor did any of the 668 exposed to SJ. However, of the 500 exposed the SJ2, 4 of the 163 snails (2%) from Ayolas, a locality in the Paraná basin, were susceptible, as were 8 of 45 (18%) from Fuente, Salto, in the Uruguay basin. These findings are similar to those of studies done in other geographic areas, where some populations of B. tenagophila do not become infected with S. mansoni while others are susceptible. The results of this study signal the possibility of the expansion of schistosomiasis into a broad region of South America in which B. tenagophila is found.

Animals↗
PubMed1996

Effect of 60Co gamma radiation on Biomphalaria glabrata (Mollusca, Gastropoda) embryos: mortality, malformation and hatching.

A study was carried out on the radiosensitivity of Biomphalaria glabrata embryos submitted to doses of 5, 10, 15, 20 and 25 Gy of 60Co during the cleavage, blastula, gastrula, young trochophore and trochophore stages. Mortality, malformation and hatching were the parameters used to evaluate the damage induced by ionizing radiation. Estimated LD50 values (15 days) showed that the cleavage stage (4.3 Gy) was approximately four times more radiosensitive than the trochophore stage (17.0 Gy). Susceptibility to malformation induction was higher in the blastula, gastrula and young trochophore stages. Several types of morphogenetic malformations were observed, such as head malformations, exogastrulas, shell malformations, and embryos with everted stomodeum, with nonspecific malformations being the most frequent. The types of malformation induced by radiation probably are not radiation-specific and do not depend on the dose applied. The dose of 15 Gy was sufficient to greatly reduce the number of hatching snails regardless of the embryonic stage irradiated. We conclude that the effect of 60Co gamma radiation on B. glabrata embryos presented a specific pattern.

Animals↗
PubMedDate not supplied

[Principal factors involved in the settlement of Biomphalaria glabrata (Say, 1818), snail intermediate host of schistosomiasis in Guadalupe (author's transl)].

Six biotopes of Biomphalaria glabrata, the snail intermediate host of schistosomiasis in Guadalupe, were investigated during one annual cycle. These six biotopes included a pond, a freshwater mangrove, a stream, a mountain lake, a "microhabitat" and a canal. These six types of biotopes were characterized by various parameters whose fluctuations reveal the main factors regulating the B. glabrata populations. The climatic factors are essential in Grande Terre and resulted in an annual development cycle well determined of all the aquatic communities. The biotic factors (Predation, competition, parasitism) are important in every type of biotope, in Grande Terre as well as in Guadalupe proper. In every type of biotope, anthropic factors are also important, but mainly in canal nets which are the principal focus of human schistosomiasis. The chemical factors themselves are less important.

Animals↗
PubMed1997

Susceptibility of three successive snail generations from positive and negative laboratory bred Biomphalaria alexandrina from different localities in Egypt to infection with Schistosoma mansoni from Giza.

Susceptibility of snail vectors to schistosome infection varies between geographical areas, populations in the same area and among individuals in the same population. It is also affected by biological factors of which are snail size (age), number and age of miracidia exposed to water, temperature, illumination and darkness. Our preview studies indicated that snails 4-6 mm in diameter exposed to 5 freshly hatched miracidia under light and in water at 25 degrees C are optimum conditions for infection of Biomphalaria alexandria from various localities in Egypt with Schistosoma mansoni (TBRI strain maintained in hamsters). In the present study, groups of 16 snails from three successive generations from positive and negative laboratory bred B. alexandrina from Giza, Alexandria, Menoufia, Cairo and Minia were exposed to S. mansoni miracidia (TBRI Strain) from Giza under the above mentioned optimum conditions. From the 20th day infection snails were checked from cercariae shedding to estimate the prepatent period and their number from each snail light for one hour. B. alexandrina from the various localities in Egypt were susceptible to S. mansoni (TBRI strain) infection. Snails from Alexandria were the most susceptible, followed by those from Cairo, Giza, Menoufia and Minia. Snails from positive generations were more susceptible to infection than those from negative ones. However, there has been a decline in the susceptibility of snails from one generation to the next. The prepatent period for shedding of cercariae was 27 days in case of snails from positive generations and it was extended to 38 days among snails from negative ones. It can be concluded that: (1) There are different levels of susceptibility between B. alexandrina from the various localities in Egypt and infection with S. mansoni from Giza. (2) Unsusceptibility (refractory character) of B. alexandrina to S. mansoni infection could be a heritable character like susceptibility. Consequently, it would be beneficial to select actively resistant snails and mass culture them to increase the proportion of alleles for insusceptibility as a possible mean for biological control of schistosomiasis in natural population.

Animals↗
PubMed1997

Phenoloxidase activity in the reproductive system of Biomphalaria glabrata: role in egg production and effect of schistosome infection.

Infection by larval trematodes often causes a cessation of egg production in its molluscan intermediate host and is referred to as parasitic castration. Because phenoloxidase (PO) has been shown to be involved in egg formation in other invertebrate species, we investigated the role of PO in normal egg production in the snail, Biomphalaria glabrata, and the effects of Schistosoma mansoni infection on the PO pathway in this snail. Our data showed that PO activity in the albumen gland (AG) is initially expressed when snails reach a size of approximately 8 mm in shell diameter and continues to increase as snails grow, indicating a developmental link between snail size and AG PO expression. Egglaying was also shown to be coincidental with the onset of PO expression in the AG, thereby supporting a direct association between PO activity and egg production. In addition, exposure of snails to diethyldithiocarbamate (DDC), a PO inhibitor, affected normal in vivo egg production, as evidenced by a significant decrease in the numbers of eggs laid in DDC-treated groups compared to nontreated groups. Normal resumption of egg-laying activity in treated snails following withdrawal of the drug indicated that inhibition was reversible. Taken together, the results of our developmental and DDC-exposure studies provide strong support for a crucial role of PO in normal egg production in this animal. Finally, AG PO activities of infected and uninfected control snails were measured over the course of S. mansoni infection. Our results showed that both total and specific enzyme activities in the AG of infected snails were significantly decreased at 28 and 33 days postinfection (PI) when compared to those of control snails. Results of subsequent experiments assessing the effects of larval infection on L-tyrosine (PO substrate) levels in AG and ovotestis revealed a significant increase in the levels of this compound in both organs over the course of infection. It is concluded that AG PO activity is functionally linked to egg formation in normal snails and that a strong association exists between parasite-mediated decrease in AG PO activity and parasitic castration. However, from the data presented, a direct causal relationship linking infection, decreased PO, and castration has yet to be established.

Animals↗
PubMed1997

Effect of aprotinin on Schistosoma mansoni miracidial penetration into biomphalaria Alexandrina.

The effect of aprotinin on Schistosoma mansoni miracidial penetration process, by its direct topical application on Biomphalaria alexandrina snails, was studied The snails were exposed to S. mansoni miracidial suspension which was mixed with aprotinin at concentrations ranging from 0.02 to 20 Kallikrein inactivator units (KIU)/ml of applied solution. Results showed that aprotinin had marked inhibitory effect on miracidial penetration of the snails. The concentration that resulted in 50% inhibition of the miracidial penetration into B. alexandrina snails (LD50) was 2.4 KIU/ml while (LD96) was 20 KIU/ml of the applied solution. Thus, aprotinin may be one of the important methods in the control of schistosomiasis.

Animals↗
PubMed1997

Infection of laboratory bred Biomphalaria alexandrina from Giza and Alexandria governorates with Schistosoma mansoni from Giza in relation to snail size and number of penetrated miracidia.

Snail size and the number of Schistosoma mansoni miracidia penetrated are two important factors among others that might influence Biomphalaria alexandrina infection with S. mansoni. Groups of 16 snails of fixed age but of different size class (2-4 mm), (4-6 mm), (6-8 mm), (8-10 mm) and (10-12 mm) from three successive generations of positive and negative laboratory bred B. alexandrina from Giza and Alexandria governorates were each exposed to five S. mansoni miracidia (TBRI from Giza) under light and in water at 25 degrees C. After 20 days, the snails were examined for cercarial shedding to determine their prepatent periods and to estimate the number of cercariae shed from each snail under light for one hour. Other groups of snails (4-6 mm) from three successive generations of positive and negative laboratory bred B. alexandrina from these two Governorates were each exposed to 3, 5, 10, 15, 20 and 25 miracidia. Snails were checked starting from the 20th day of infection to assess whether or not they had acquired infection. The infection rate of B. alexandrina from Giza and Alexandria governorates and their generations decreased significantly as the snail size increased while it increased significantly as the number of miracidia increased. However, there has been a decline in the susceptibility of snails from one generation to the next. The prepatent period for the shedding of cercariae was long in large sized snails and from those descending from negative snails. It can be concluded that the infection rate of B. alexandriina snails is affected by snail size and the number of miracidia penetrated.

Animals↗
PubMed1976

The karyotype of Biomphalaria glabrata, the snail vector of Schistosoma mansoni.

Karyotyping was done on the mitotic metaphase chromosomes obtained from the embryos of Biomphalaria glabrata. The 18 chromosome pairs were identified and classified into 6 groups. The diploid cell has 10 pairs of metacentric, 4 pairs of submetacentric, 2 pairs of acrocentric and 2 pairs of telocentric chromosomes. The pair number 8 with secondary constriction can be used as a marker in genetic experiments.

Animals↗
PubMed1998

Schistosoma mansoni infection inhibits maturation of ovotestis allografts in Biomphalaria glabrata (Mollusca:Pulmonata).

The posterior tip of juvenile snails, consisting of immature ovotestis, vesicular connective tissue, and digestive gland acini, all surrounded by body wall, was implanted into the hemocoel of allogeneic adult Biomphalaria glabrata. Recipient snails were either uninfected or had been infected 15 days previously with Schistosoma mansoni. Graft recipients were dissected at 30 or 60 days postimplantation (DPI), and the implants, along with preimplantation controls, were examined histologically. The gonads in preimplantation controls consisted of a partially coiled collecting canal partitioned dorsally by connective tissue septa and contained mainly spermatogonia-like cells and small oocytes. In uninfected recipients, implanted gonads underwent rapid development, i.e., had formed mature acini and were carrying out vigorous gametogenesis, both spermatogenesis and oogenesis, by 30 DPI. At 60 DPI, numbers of spermatozoa had increased substantially in most implants. In infected recipients, relatively little development or gametogenesis occurred at either 30 or 60 DPI, and oogenesis was more strongly inhibited than spermatogenesis. Except for 1 implanted gonad (out of 25) that had undergone necrosis at 60 DPI and a second otherwise healthy 60-day implant partially encapsulated at its cut surface (both in uninfected recipients), no significant hemocytic response occurred against the allografts.

Animals↗
PubMed1976

Studies on resistance in snails. 7. Evidence of interference with the defense reaction in Biomphalaria glabrata by trematode larvae.

Echinostoma lindoense sporocysts that develop from irradiated miracidia normally are destroyed by amebocyte capsules in the ventricle of Biomphalaria glabrata within 10 days postexposure. The survival period of these ventricular sporocysts was considerably longer in snails that also harbored normal sporocysts of E. lindoense, Paryphostomum segregatum, or Schistosoma mansoni. Protection of irradiated E. lindoense sporocysts by the same of different trematode species is presumed to be the result of an active process by which normal sporocysts interfere with capsule formation and protect themselves and other trematode larvae from encapsulation. Homologous protection was stronger than heterologous.

Animals↗
PubMed1998

Heritable non-susceptibility in an allopatric host-parasite system: Biomphalaria glabrata (Mollusca)-Echinostoma caproni (platyhelminth Digenea).

We studied the heritability of adult nonsusceptibility/susceptibility in an allopatric host-parasite system, Biomphalaria glabrata (Brazil)-Echinostoma caproni (Egypt). In this system, the fitness of the infected host is substantially reduced because of castration. Mean frequencies of susceptibility among progeny of individual susceptible or nonsusceptible parents were compared, and heritabilities of susceptibility and nonsusceptibility were calculated under a quantitative genetic model. A Monte-Carlo simulation was used to assess the significance of the heritability estimates under the hypothesis of normal standard deviation. The results showed high heritability of both nonsusceptibility (0.56) and susceptibility (0.91).

Animals↗
PubMed1994

[Importance of Tarebia granifera in the control of a population of Biomphalaria peregrina introduced in Cuba].

It was observed that the Tarebia granifera plays a significant role in the control of a Biomphalaria peregrina population introduced in a permanent water body. The densities of this planorbid, which had reached high levels, were notably reduced by two important events: an increase of the water level due to heavy rains, and the introduction of the competitor, whose effectiveness had been tested in a different habitat. Knowledge on the ecology and biology of the competitor and the host in permanent water bodies helped to elaborate the measures of control which led to the reduction of the host densities while those of the competitor increased.

Animals↗
PubMed1994

[Study of the molluscicide activity of different plants on Biomphalaria havanensis, potential intermediary host of schistosomiasis in Cuba].

Various experimental studies were carried out with plants of the Compositae, Verbenaceae, Polygonaceae and Agavaceae families to determine their molluscicidal capacity. Molluscicidal activity on Biomphalaria havanensis was detected in plants of the Agavaceae family. The plants employed in the experiment were Agave fourcroydes and Agave franzosinii. Lethal doses were determined. These were: LD50 = 12.45 and LD90 = 22.88 mL/L, for A. fourcroydes and LD50 = 8.78 and LD90 = 15.91 mL/L, for A. franzosinii. No decrease was observed in the effectiveness of the aquous extracts with the passing of time. Solar radiation did not seem to effect the molluscicidal activity of the plant extracts.

Animals↗