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PubMed2004

A comparative toxicologic and genotoxic study of the herbicide arsenal, its active ingredient imazapyr, and the surfactant nonylphenol ethoxylate.

The herbicide arsenal 250 NA, its technical-grade active ingredient imazapyr, and the surfactant nonylphenol ethoxylate (NP) were evaluated through genotoxicity and toxicity studies in different organisms. A comparative study of these three compounds was carried out to assess how the addition of surfactant components may pose the highest toxicological risk to pesticide formulations. The results showed that arsenal, imazapyr, and NP did not cause chromosome aberration in Allium cepa nor increase the frequency of micronuclei in mice. However, toxicological evaluations showed that NP was the most toxic compound to mice, A. cepa, Drosophila melanogaster, and Biomphalaria tenagophila. In this evaluation, it was observed that the adverse effects were produced by the surfactant additive of the pesticide formulation.

Animals↗
PubMed2006

Differential effects of paraquat on oxidative stress parameters and polyamine levels in two freshwater invertebrates.

Paraquat is still a widely used herbicide in several countries. Its toxic action on plants occurs through a one-electron reduction interfering with the photosynthesis process. By a similar reaction, the herbicide may induce peroxidation processes in non-target animal species. Furthermore, paraquat may interfere with the cellular transport of polyamines. The aim of this work was to investigate some aspects related to paraquat-induction of oxidative stress (lipoperoxidation, enzymatic activities of catalase and superoxide dismutase) and also the levels of polyamines (putrescine, spermidine and spermine) in two species of freshwater invertebrates, the oligochaete Lumbriculus variegatus and the gastropod Biomphalaria glabrata. The results showed that both organisms elicited differential responses. In addition, the data suggested that polyamines may play an important role against lipoperoxidation processes.

Animals↗
PubMed2005

Echinostoma paraensei: differential gene transcription in the sporocyst stage.

The sporocyst stage of trematode development plays the crucial role of establishing a successful infection in the molluscan intermediate host. Due to the small size and presence of this stage within the tissues of the host, much of our current knowledge of sporocyst biology relies on cultured specimens. To gain insight into the transcriptional patterns of early sporocysts, suppression subtractive hybridization was employed to identify 69 unique expressed sequence tags likely to be upregulated in cultured sporocysts of Echinostoma paraensei, a trematode parasite of the planorbid snail, Biomphalaria glabrata. Upwards of 70% of the unique sequences were not identified by homology to known genes. However, one transcript may encode an inhibitor of nitric oxide synthase, indicating a possible role in protection against host defense mechanisms. An array containing the majority of the sequenced clones was probed with in vivo-derived cDNA, confirming for the first time in vivo expression of putative sporocyst genes. However, qPCR quantification demonstrated significant reductions in transcription rates in cultured versus in vivo sporocysts for three of six transcripts tested. Additionally, five of the six tested transcripts demonstrated significant variation in expression over the entire life cycle, with the significant upregulation occurring during early intramolluscan development or in the free-living stages immediately preceding snail penetration, confirming the efficacy of the SSH technique.

Animals↗
PubMed2005

Hemozoin formation in Echinostoma trivolvis rediae.

Rediae of the trematode Echinostoma trivolvis, from naturally infected Helisoma trivolvis snails, form a black pigment while inside the snail host. Here we examine the black pigment to show that the insolubility characteristics in detergent and weak base solution are identical to Plasmodium falciparum hemozoin. Laser desorption mass spectrometry of the purified pigment demonstrates the presence of heme. Examination of purified pigment under polarized light microscopy illuminates ordered birefringent crystals. Field emission in lens scanning electron microscopy reveals irregular ovoid crystals of 200-300 nm in diameter. The purified pigment crystals seeded extension of monomeric heme onto the crystal which by Fourier Transform Infrared analysis is beta-hematin. Rediae of a second echinostome parasite, Echinostoma caproni, from experimentally infected Biomphalaria glabrata, do not produce measurable or recoverable heme crystals. These observations are consistent with heme crystal formation by a hematophagous parasite within a non-vertebrate intermediate host.

Animals↗
PubMed2005

Molecular data suggest that microsporidian parasites in freshwater snails are diverse.

Microsporidian parasites infect almost all invertebrate and vertebrate hosts and have significant effects on individual and population fitness. Phylogenetic analysis demonstrates that the phylum is highly divergent and that some lineages show strong associations with host taxa. We here examine the diversity and distribution of parasites in gastropod molluscs to test for host-parasite co-association. 16 populations representing 10 species of freshwater snails were screened using microsporidian specific small subunit rDNA primers. Four novel microsporidian parasite sequences were detected within populations of three host species from the genera Bulinus, Biomphalaria and Planorbis. Prevalence ranged from 5 to 84%. Phylogenetic analysis of these novel sequences reveals that they group together as a paraphyletic assemblage in the microsporidian tree basal to the two lineages containing the genera Encephalitozoon and Nosema. Preliminary observation of one microsporidian infection, show parasites distributed in all tissue systems of Bulinus globosus. However, infection is most prevalent in the digestive gland while also in the egg sacs, suggesting that the microsporidium is using a mixed strategy of horizontal and vertical transmission in this population.

Animals↗
PubMed2005

A study of the larvicidal and molluscicidal activities of some medicinal plants from northeast Brazil.

In a search for natural products that could be used to control the vectors of tropical diseases, 23 extracts of medicinal plants from the northeast of Brazil have been tested for molluscicidal activity against egg masses and adults of the snail Biomphalaria glabrata, for larvicidal activity against the larvae of the mosquito Aedes aegypti, and for general toxicity against the larvae of the brine shrimp Artemia salina. Of these extracts, two were active against the adult snail, one against snail egg masses, eight against the larvae of the mosquito, and 16 showed toxicity towards the brine shrimp. Chemical tests indicated that a wide variety of natural product classes were present in those extracts that showed significant activities in the bioassays.

Aedes↗
PubMed2005

Comparative study on two freshwater invertebrates for monitoring environmental lead exposure.

Two freshwater invertebrate organisms, Biomphalaria glabrata and Lumbriculus variegatus, were tested as potential experimental animal models to assess Pb exposure using acute laboratory bioassays. Since long, the enzyme delta-aminolevulinic acid dehydratase (ALA-D) has been recognised as a useful biomarker of Pb exposure and effect. Therefore, determinations of ALA-D activity were performed in the whole body soft tissues of pigmented and non-pigmented gastropods B. glabrata and in the oligochaete L. variegatus. The organisms were exposed to varying concentrations of Pb for 48 h. Levels of Pb in the invertebrates were also analysed. Highly significant negative correlations were found between the enzymatic activity and the levels of Pb exposure, and also between the enzymatic activity and the metal incorporated by the invertebrates. No significant differences were found in the enzyme activity nor in the resulting metal accumulation based on gastropod pigmentation. The values of Pb concentration that produce 50% of inhibition on the enzyme activity (EIC50) were 0.023 and 0.029 mg Pb/L for pigmented and non-pigmented B. glabrata, respectively. A much higher value was found for L. variegatus (0.703 mg Pb/L). The non-observed effect concentration (NOEC) on enzyme activity for the oligochaetes was 0.05 mg Pb/L, about twice the EIC50 calculated for the gastropods. These data showed that both pigmented and non-pigmented B. glabata were much more sensitive organisms than the oligochaetes. The differences in enzyme inhibition could be attributed, at least partly, to differences in the metal body burden found between the organisms, since levels of Pb accumulated by B. glabrata were approximately three times higher compared to those observed in L. variegatus. Therefore B. glabrata showed to be a more suitable and reliable bioindicator organism for assessing Pb contamination in aquatic ecosystems, especially at low levels of metal exposure.

Animals↗
PubMed2006

Development of molecular approaches for the identification of transmission sites of schistosomiasis.

Primers targeting the gene encoding the small subunit rRNA were designed to amplify DNA from Schistosoma mansoni with high specificity. Three PCR systems were developed: conventional PCR, two-step nested PCR (NPCR) and single-tube nested PCR (STNPCR). The limits of detection of parasite DNA for the conventional PCR, NPCR and STNPCR were 10 pg, 0.1 fg and 1 fg, respectively. The assays were highly specific for S. mansoni and did not recognise DNA from closely related non-schistosome trematodes. Using pools of Biomphalaria molluscs, PCR, NPCR and STNPCR were positive in 6/16 (37.5%), 15/16 (93.8%) and 13/16 (81.3%) of the tested samples, respectively, whereas the observation of cercariae shedding after exposure to light was able to detect S. mansoni infection in 6/16 (37.5%) of the pools. Thus, the molecular detection systems had a higher level of sensitivity than standard screening of intermediate hosts by cercarial shedding when DNA was purified from pools of snails collected from endemic areas. These PCR protocols have potential to be used as tools for monitoring of schistosome transmission.

Animals↗
PubMed2000

Biological control of the snail hosts of schistosomiasis in areas of low transmission: the example of the Caribbean area.

The biological control of schistosomiasis has already proven its efficiency in several habitats in the Caribbean area. Two main types of biological control agents, either trematode parasites or competitor snails have been studied and tested against the snail hosts of schistosomiasis in this region. The first one, Ribeiroia guadeloupensis, a trematode sterilizing Biomphalaria glabrata was successfully tested in a Guadeloupean pond housing a natural population of B. glabrata. The second agent involves several species of competitor snails belonging to the Ampullariidae (Pomacea glauca, Marisa cornuarietis) and Thiaridae (Tarebia granifera, Melanoides tuberculata) families. Ampullarid snails were tested with success in several West Indian islands such as Guadeloupe. Thiarid snails have also proven their efficiency but also their limits in several types of habitats in Guadeloupe, Martinique, St. Lucia and Venezuela. Competitor snails have also proven to be useful in preventing the recolonization by the snail hosts after molluscicide treatments. The case of the rivers of the littoral central part of Venezuela is particularly relevant to this issue. The island of Martinique also constitutes a good example of the importance of competitor snails in a post-transmission phase of schistosomiasis control. This island is a well-developed country where schistosomiasis transmission was interrupted in the 1970s. However, the reactivation of some transmission sites was observed in the 1980s. The introduction of M. tuberculata into these sites resulted in the interruption of transmission and the near total disappearance of the snail hosts. Presently, the thiarid snails have colonized the whole Martinican hydrographic system and maintain dense populations preventing an eventual recolonization by the planorbid snails and thus are maintaining a sustainable control.

Animals↗
PubMed1999

Population biology of Schistosoma mansoni in the black rat: host regulation and basic transmission rate.

A simple mathematical model was built to investigate the population biology of Schistosoma mansoni in its natural definitive host, the black rat (Rattus rattus). Prevalence and parasite abundance over 13 years from field studies and data from laboratory experiments were used to set up the model. Sensitivity analysis showed that the abundance of parasites is strongly influenced by variation in the values of infection parameters. The model shows that the parasite is able to control populations of definitive hosts. We discuss the factors that may explain the long-term persistence of S. mansoni among its natural definitive host, R. rattus and its intermediate host, the snail Biomphalaria glabrata in Guadeloupe (French West Indies). The impact of the parasite does not appear to explain the apparent persistence of the host-parasite association over a 13 year period. Our results seem to support the influence of environmental factors, which may act on the infection process by reducing, or increasing, the rate of encounters between hosts and free-living stages of the parasite.

Animals↗
PubMed2000

Molluscicidal and piscicidal activities of Venezuelan Chrysobalanaceae plants.

Extracts of increasing polarity of 6 Venezuelan plants belonging to the Chrysobalanaceae family were tested for possible letal toxicity against Biomphalaria glabrata Say, a snail intermediate hosts of Schistosoma mansoni Sambon. The piscicidal toxicity of the active extracts was also evaluated with the aim of findings compounds without toxicity in nontarget organisms, principally fishes and humans.

Animals↗
PubMed1994

Molluscicidal saponins from a Zimbabwean strain of Phytolacca dodecandra.

Three new monodesmosidic saponins, all glycosides of 2 beta-hydroxyoleanolic acid, were isolated from an aqueous extract of a Zimbabwean strain of Phytolacca dodecandra. Their structures were, mainly by spectroscopic methods (LSIMS, 1H NMR, COSY, NOESY, TOCSY, J-resolved 1H NMR, 13C NMR, HETCOR), established as 3-O-[2',4'-di-O-(beta-D-glucopyranosyl)-beta-D-glucopyranosyl]2 beta-hydroxyoleanolic acid, 3-O-[O-alpha-L-rhamnopyranosyl-(1-->2)-O-[beta-D-galactopyranosyl- (1-->3)]-beta-D-glucopyranosyl]2 beta-hydroxyoleanolic acid and 3-O-[3'-O-(beta-D-galactopyranosyl)-beta-D-glucopyranosyl]2 beta-hydroxyoleanolic acid. Two of the saponins were submitted to a preliminary screening for molluscicidal activity against the schistosomiasis transmitting snail Biomphalaria glabrata and showed, respectively, strong and weak activity. In addition, four saponins previously reported from other strains of Phytolacca dodecandra were identified.

Animals↗
PubMedDate not supplied

Royal Society of Tropical Medicine and Hygiene meeting at Manson House, London, 18 May 1995. The epidemiology of human schistosomiasis in the Senegal river basin.

Extensive water development has taken place in the north of Senegal over the last decade, resulting in a large increase in the amount of fresh water for irrigation. The objectives of the present study were to determine the prevalence and intensity of Schistosoma mansoni and S. haematobium in the Senegal river basin (SRB), and to ascertain the distribution of the snail species acting as intermediate hosts for both species of schistosomes. The schistosomiasis survey started in January 1994 and was completed in March 1995. Compared to studies before the construction of the Diama dam, there was a significant increase in both the prevalence and intensity of urinary and intestinal schistosomiasis in the human population in parts of the SRB. From the 9014 people who were registered from 180 villages and 4 towns (10 districts), 7750 were examined. S. mansoni was found in the lower valley (lower delta-Senegal river, lower delta-Lampsar river, upper delta, and diéré) but not in the middle valley. The mean prevalence ranged from 4.4% in the lower delta-Senegal River to 71.8% in the zone of Lac de Guiers, where prevalence and intensity of infection were higher on the eastern side of the lake (81.3% with a mean number of 2088 eggs/g of faeces) compared with the western side (50.3% with a mean 1111 eggs/g). S. haematobium was recorded throughout the area of study, ranging from a mean prevalence of 0.37% in diére (lower valley) to 41.5% in the lower valley (Lampsar river), where the mean egg count was 313/10 mL of urine. Physical and chemical changes to the environment have favoured the spread and increase in the populations of freshwater snails. The only snail involved in the transmission of S. mansoni was Biomphalaria pfeifferi. Five species of bulinid snails were present--Bulinus globosus, Bu. umbilicatus, Bu. senegalensis, Bu. forskalii and Bu. truncatus--but only the first 3 species were involved in the transmission of S. haematobium in the lower and middle valleys.

Adolescent↗
PubMedDate not supplied

Schistosomiasis in northern Mozambique.

A survey of 12 schools in Cabo Delgado, northern Mozambique, was performed to assess the extent of schistosomiasis infection. Questionnaires validated by parasitological examination of stools and urine were used. Very high prevalences of Schistosoma haematobium infection were found in all schools (77.5% was the lowest recorded), so the questionnaires did not distinguish 'high risk' schools. However, they clearly indicated a good knowledge of the infection by students and teachers. The disease was recognized by teachers to be a public health problem in the area. S. mansoni infection was rare. It had not been reported in previous surveys, but its vector Biomphalaria was discovered in the area. Revised mapping of the disease is advisable in view of probable changes after many years of conflict.

Adolescent↗
PubMed1996

Identification of the first major allergen of a squid (Todarodes pacificus).

BACKGROUND: In Japan, squid is an important seafood, and some patients with food allergies are sensitive to squid. There has been no report, however, describing the major allergens of squid. OBJECTIVE: To characterize squid allergens, we isolated a major allergen from the Pacific flying squid (Todarodes pacificus) and compared it with a major allergen from a shrimp (Penaeus orientalis). METHODS: The major squid and shrimp allergens were isolated by column chromatography on diethylaminoethyl-Sepharose (Pharmacia, Uppsala, Sweden), hydroxylapatite, and Sephacryl S-300 (Pharmacia). The IgE reactivity of the isolated allergens was assessed by immunoblotting. The cross-reactivity between the squid and shrimp allergens was examined by use of mouse polyclonal and monoclonal antibodies to the major allergens. Amino acid sequence analyses of the isolated allergens were done. RESULTS: The isolated squid allergen is a 38 kd, heat-stable protein. IgE antibody binding to the purified squid allergen was demonstrated by immunoblotting. Cross-reactivity between major squid and shrimp allergens was demonstrated with sera from patients allergic to squid or shrimp or with allergen-specific monoclonal antibodies. The amino acid sequence analysis of the major squid allergen showed a marked homology with tropomyosin from blood fluke planorbid (Biomphalaria glabrata), which is a common vector snail of Schistosoma mansoni. CONCLUSION: This 38 kd protein is a major allergen of the squid, Todarodes pacificus, and is believed to be squid muscle protein tropomyosin. We named it Tod p 1 according to International Union of Immunological Societies allergen nomenclature regulation.

Allergens↗
PubMedDate not supplied

Novel laboratory approaches to multi-purpose aquatic bioregenerative closed-loop food production systems.

Based on the construction principle of the Closed Equilibrated Biological Aquatic System (C.E.B.A.S.) two novel combined animal-plant production systems were developed in laboratory scale the first of which is dedicated to mid-term operation in closed state up to two years. In principle both consist of the "classic" C.E.B.A.S. subcomponents: animal tank (Zoological Component), plant cultivators (Botanical Component), ammonia converting bacteria filter (Microbial Component) and data acquisition/control unit (Electronical Component). The innovative approach in the first system is the utilization of minimally three aquatic plant cultivators for different species. In this one the animal tank has a volume of about 160 liters and is constructed as an "endless-way system" surrounding a central unit containing the heat exchanger and the bacteria filter with volumes of about 1.5 liters each. A suspension plant cultivator (1 liter) for the edible duckweed Wolffia arrhiza is externally connected. The second plant cultivator is a meandric microalgal bioreactor for filamentous green algae. The third plant growth facility is a chamber with about 2.5 liters volume for cultivation of the "traditional" C.E.B.A.S. plant species, the rootless buoyant Ceratophyllum demersum. Both latter units are illuminated with 9 W fluorescent lamps. In the current experiment the animal tank contains the live-bearing teleost fish Xiphophorus helleri and the small pulmonate water snail Biomphalaria glabrata because their physiological adaptation to the closed system conditions is well known from many previous C.E.B.A.S. experiments. The water temperature is maintained at 25 degrees C and the oxygen level is regulated between 4 and 7 mg/l by switching on and off the plant cultivator illuminations according to a suitable pattern thus utilizing solely the oxygen produced by photosynthesis. The animals and the microorganisms of filter and biofilm provide the plants with a sufficient amount of carbon dioxide. Oxygen concentration, pH value, temperature and redox potential are on-line recorded. Ion concentrations and numbers of living germs in the system water are determined twice monthly in the laboratory from samples taken from a special "sample removal module"; the sample volume is automatically replaced from an reservoir container. A rotatory pump produces a water flow of about 38 l/min. For a similar smaller test system with approx. 10 l volume developed from the C.E.B.A.S.-MINI-MODULE a novel indirect solar energy supply is tested which has a buffer capacity to maintain the system for 7 days in darkness under central European climate conditions also in winter. It contains only a single plant cultivator which is operated with Wollfia arrhiza. This lemnacean plant is able to produce large amounts of plant biomass in a short time by vegetative reproduction via daughter fronds. This easy-to-handle apparatus is dedicated to be operative more than 4 month. The experimental animals and microorganisms are the same as in the large system. The paper provides detailed information on the system construction principles and the biological, physical and chemical data of the initial phase of the test runs of both systems with the main focus on the large one.

Animals↗
PubMed1982

Lectin-induced modulation of snail hemocyte surface determinants: clearance of Con A-receptor complexes.

The fate of surface concanavalin A (Con A)-receptor complexes on hemocytes from two stocks of the snail, Biomphalaria glabrata (PR albino and 10-R2), was studied using both direct (Con A-FITC) and indirect (biotin-Con A, avidin-FITC) fluorescent staining methods. The results of experiments in which living hemocytes were exposed first to biotin-Con A, followed by fixation and subsequent treatment with avidin-FITC to localized surface-bound lectin, demonstrate that Con A complexes are rapidly cleared from hemocyte plasma membranes. Experiments employing Con A-FITC further indicate that clearance is accomplished through an internalization process whereby Con A-complexes are endocytosed and eventually accumulate as a single intracellular aggregate of fluorescent material in the cell body of each hemocyte. In addition, a redistribution of surface complexes into patches and caps is concomitant with receptor clearance, with a maximum frequency of patching (approx. 45%) and capping (approx. 30%) occurring within 5 and 10 min., respectively, of initial Con A exposure. PR albino and 10-R2 snail hemocytes appear indistinguishable with regards to their responsiveness to Con A-binding. The close similarity in the behavior of Con A complexes or circulating hemocytes from both snail stocks further support the conclusion that Con A-reactive determinants and their associated membrane components probably represent identical molecular populations on PR albino and 10-R2 B. glabrata blood cells.

Analysis of Variance↗
PubMedDate not supplied

Integrin-like RGD-dependent binding mechanism involved in the spreading response of circulating molluscan phagocytes.

Circulating phagocytic cells (hemocytes) of the snail Biomphalaria glabrata, intermediate host of the human blood fluke Schistosoma mansoni, were treated with the tetrapeptide, arg-gly-asp-ser (RGDS), an integrin-specific adhesion inhibitor, and assessed for their ability to adhere and spread on uncoated and snail plasma protein-coated glass slides. Although cells were capable of adherence, RGDS significantly inhibited the spreading ability of hemocytes in both a time and RGDS concentration-dependent fashion regardless of plasma protein coating. The inhibition of hemocyte spreading by RGDS was a specific response, since treatment of cells with a glutamic acid-substituted control peptide (RGES) did not exert the same inhibitory effect. A comparison of RGDS-responses between hemocytes of two strains of B. glabrata, one resistant (R; 13-16-R1 strain) and the other susceptible (S; NMRI strain) to infection by S. mansoni, revealed several snail strain-specific differences. At concentrations of 0.5 mM RGDS, R snail hemocyte spreading was unaffected, whereas a significant depression of spreading was seen in cells of the S snail. Moreover, we observed that R strain hemocytes spread more rapidly on homologous plasma-coated surfaces than the S snail strain following peptide pretreatment and removal. These data suggest that hemocytes from S and R snails may differ either in the number of RGDS-binding receptors or in their affinity for the RGDS peptide. In order to identify the type(s) of integrin-like RGD-binding receptors that may be present on the surface of snail immunocytes, washed hemocytes were placed on various mammalian extracellular matrix proteins and evaluated for their spreading function in the presence of specific or non-specific peptides. Hemocyte aggregation or clumping was observed on all test protein substrates, and this aggregation behavior was specifically inhibited by RGDS. Thus, RGD-binding receptors appear to play a critical role in cellular motility on matrix-coated surfaces and/or cell-cell binding. Our data provide functional evidence for an integrin-like receptor on circulating phagocytes of snails, and for an RGD-binding mechanism involved in cell-substrate interactions.

Animals↗