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PubMed2005

Application of synchrotron-radiation-based computer microtomography (SRICT) to selected biominerals: embryonic snails, statoliths of medusae, and human teeth.

Synchrotron-radiation-based computer microtomography (SRmicroCT) was applied to three biomineralised objects First, embryonic snails of the freshwater snail Biomphalaria glabrata, second, rhopalia (complex sense organs) of the medusa Aurelia aurita, and third, human teeth. The high absorption contrast between the soft tissue and mineralised tissues, i.e. the shell in the first case (consisting of calcium carbonate) and the statoliths in the second case (consisting of calcium sulphate hemihydrate), makes this method ideal for the study of biomineralised tissues. The objects can be non-destructively studied on a micrometre scale, and quantitative parameters like the thickness of a forming a snail shell or statolith crystal sizes can be obtained on a length scale of 1-2 mum. Using SRmicroCT, the dentin-enamel border can be clearly identified in X-ray dense teeth.

Animals↗

PubMed2002

Lead toxicity, locomotion and feeding in the freshwater snail, Lymnaea stagnalis (L.).

The effects of lead (5 or 10 ppm) on the survival of the freshwater snail Lymnaea stagnalis (L.) collected from lead contaminated or uncontaminated environments were evaluated under controlled laboratory conditions. The animals from the contaminated environment had significantly greater survivability than those from the unpolluted environment to subsequent acute (up to 24 days) exposure to lead. Acute (72 h) exposure to lead inhibited several behavioural activities including locomotion, feeding, tentacle extension and emergence from the shell. Lead bioaccumulated in the snail tissues, especially the buccal mass and stomach. The freshwater snail provides a valuable system for studying the bioaccumulation and development of tolerance to environmental lead.

Animals↗

PubMed1981

A possible relationship between lattice and snail track degenerations of the retina.

We studied 1,000 eyes of 500 subjects in an attempt to discover a relationship between lattice and snail track degenerations of the peripheral retina. Because of the clinical similarities between these two degeneration lesions, we suggest that snail track degeneration is either a variant of or an early stage of lattice degeneration. Long-term follow-up of eyes with snail track degeneration is essential to detect any morphologic alteration in the lesions suggesting lattice degeneration.

Adolescent↗

PubMed1989

Trichobilharzia ocellata: influence of infection on the interaction between the dorsal body hormone, a female gonadotropic hormone, and the follicle cells in the gonad of the intermediate snail host Lymnaea stagnalis.

Activation of adenylate cyclase (AC)-cAMP system in follicle cells of Lymnaea stagnalis by the gonadotropic dorsal body hormone (DBH) is inhibited by schistosomin, an agent present in hemolymph of snails infected with Trichobilharzia ocellata. AC activation was determined enzyme cytochemically. This conclusion is based on the observation that the percentage of oocytes with AC-positive follicle cells in gonads incubated in the presence of schistosomin, i.e., in serum of infected snails (IS) with DBH, is significantly lower than that in gonads incubated in the absence of schistosomin, i.e., in serum of noninfected snails (NS) with DBH. Follicle cells in gonads preincubated in the absence of schistosomin, i.e., in NS, and subsequently incubated with freshly dissolved DBH showed a considerably lower response to DBH than those in not preincubated gonads. This indicates that the number of receptors for DBH on follicle cells had decreased during preincubation. The response to DBH also appeared to decrease when the hormone was preincubated in NS. This indicates that the activity of DBH decreases during preincubation. These data make it impossible to answer the question of whether or not schistosomin acts as an antagonist of DBH at the receptor level.

Adenylyl Cyclases↗

PubMed1979

Enzyme analyses of Bulinus africanus group snails (Mollusca: Planorbidae) from Tanzania.

38 population samples of snails of the Bulinus africanus group, collected from three separate areas of Tanzania, have been examined. Enzymes in crude digestive gland extracts of individual snails have been analysed by isoelectric focusing in polyacrylamide gels. The enzymes studied were: malate dehydrogenase (MDH); phosphoglucomutase (PGM); glucosephosphate isomerase (GPI); acid phosphatase (AcP) and hydroxybutyrate dehydrogenase (HBDH). Samples of B. nasutus were clearly differentiated from other species and enzyme differences were apparent between samples from the lake and coastal areas. Similarly, although clear distinctions could not always be made, samples of B. africanus, B. globosus and B. ugandae were characterized by their enzyme types. Individual variation was detected within populations and the significance of enzyme polymorphisms in relation to identification has been considered. No correlation was found between snail enzyme type and susceptibility to Schistosoma haematobium or S. bovis.

Acid Phosphatase↗

PubMed1985

Verification of the membrane hypothesis of aging on the identified giant neurons of the snail Lymnaea stagnalis L. (Gastropoda, Pulmonata) by a combined application of intracellular electrophysiology and X-ray microanalysis.

The validity of the membrane hypothesis of aging (Zs.-Nagy, 1978) was tested on identified giant neurons of the snail Lymnaea stagnalis L. by using a combination of intracellular microelectrophysiology and X-ray microanalysis of the intracellular water and electrolyte concentrations on the very same cells. The snails were taken from an inbred stock and divided into young, adult and old age groups (3, 12 and 24 mth, respectively). The giant neuron called LPa-2 from the left parietal ganglion was selected for the studies. The resting potential of the cell membrane was recorded by means of intracellular microelectrode technique. The very same cells were then explored by freeze fracture and analyzed by an energy dispersive bulk specimen method of X-ray microanalysis. The resting membrane potential displayed an age-dependent hyperpolarization, the intracellular water content decreased considerably and the intracellular potassium concentration increased almost 90% by old age. The relative passive permeability ratio for potassium (PK) and chloride (PCl) was calculated from the measured data by means of the Goldman-Hodgkin-Katz equation. Such calculations revealed that PK decreases nearly 50% with age causing the increase of the intracellular potassium content, and this is accompanied also by a significant decrease of the PCl. The results support the validity of the membrane hypothesis of aging and are in agreement with the general knowledge regarding the electrophysiological behaviour of the giant neurons of Gastropode snails.

Aging↗

PubMed1990

The epidemiology of schistosome infections of snails: taking the theory into the field.

Most field studies of the epidemiology of schistosome infections of snails have been essentially descriptive in nature. Although much use has been made of epidemiological models in the interpretation of experimental studies of schistosome-snail interactions, the models have had restricted application outside the laboratory. Here, Mark Woolhouse and Steve Chandiwana make use of a theoretical framework in discussing current understanding of schistisome-snail epidemiological patterns in the field, and then consider the implications of the analysis for the control of schistosomiasis.

Journal Article↗

PubMed1996

Accumulation of Zn, Cu, Pb and Cd in the garden snail (Helix aspersa): implications for predators.

Accumulation of Zn, Cu, Pb and Cd was studied in snails fed for 120 days on diets contaminated with each metal separately and with all metals mixed together. The concentrations of Zn in food were in the range 39 to 12 200 mg kg(-1), Cu 9-1640 mg kg(-1), Pb 0.4-12 700 mg kg(-1), and Cd 0.16-146 mg kg(-1) on a dry weight basis. At the highest concentrations of all metals the consumption rates decreased significantly. For the remaining concentrations, Zn and Cu were accumulated in soft tissue in proportion to their concentrations in food. The lowest treatments of Pb and Cd did not cause any increase in soft tissue concentrations of these metals but at average treatments, a clear increase was observed. Copper was accumulated especially efficiently, exceeding concentrations in food throughout the whole range of treatments. Except for the lower end of experimental treatments, Zn was accumulated approximately in direct proportion to its concentration in the diet. Lead was the most efficiently regulated metal, with soft tissue concentrations always substantially lower than in food. Approximately 60% of Zn, 90% of Cu, 43% of Pb and 68% of Cd on average was assimilated from food. The assimilation efficiency of food alone was ca 74%. The concentrations of metals in shells increased significantly with exposure, but (with one exception) the concentrations in shells did not exceed 5% of those found in soft tissue. We argue that snails are more important as agents of food-chain transport of Cu and Cd, than of Zn or Pb. Our results indicate also that snails are not able to deposit significant quantities of metals in their shells, at least during the time scale of our laboratory experiment.

Journal Article↗

PubMed1989

The biochemical ecology of Biomphalaria glabrata, a snail host of Schistosoma mansoni: short chain carboxylic and amino acids as phagostimulants.

1. A buccal mass olfactometer was used to investigate the responses of the fresh-water pulmonate snail Biomphalaria glabrata to carboxylic and amino acids. 2. The snails proved very discriminating as only 6 (14.6%) of the 41 chemical species tested were effective as phagostimulants. These are ranked as follows in order of potency:- butanoate greater than propanoate greater than D-malate greater than 2-hydroxybutanoate = L-tartrate = L-aspartate. 3. The structure-activity relationships of the active compounds, and their significance to the ecology and control of the snails are discussed.

Amino Acids↗

PubMed1986

The uptake and distribution of radioselenium in the larvae of Fasciola hepatica and its snail host Lymnaea columella.

Radiolabeled metacercariae of Fasciola hepatica were obtained in vivo by incubating infected Lymnaea columella snails with 20 muCi radioselenomethione (75Se-M) per snail in 5 ml of water for 5 h, or in vitro by incubating a batch of unlabeled F. hepatica metacercariae with 75Se-M for 24 h. Radioassay showed that only 5% of the 75Se-M was incorporated into maritas (juvenile flukes) from the in vivo labeled metacercariae. The inner cyst wall of in vivo labeled metacercariae contained 46% of the total activity, of which 21% was dissolved in the excysting medium. The outer, tan-colored cyst wall contained 49% of the radioactivity. Through diffusion/attachment, maritas from in vitro labeled metacercariae could occasionally be labeled with 0.4% of the total radioactivity. However, the activity was lost after inoculation into the body of mice. The outer and inner cyst walls of in vitro labeled metacercariae contained 92% and 7.6%, respectively, of the total activity. Microautoradiography demonstrated that 75Se-M was evenly distributed in the body of marita and the cyst wall of inner and outer layers from an in vivo labeled metacercaria. A 9 X 4 micron rectangularly-shaped aggregate of Ag degree grains was present on the outer periphery of the inner cyst wall. Microautoradiography of in vitro labeled metacercariae demonstrated a significant concentration of Ag degree grains on the cyst walls. The ventral plug contained fewer Ag degree grains per unit area compared to the other portion of the inner cyst wall. Uptake and distribution of 75Se-M in the snail host were also studied. It appeared that rediae and cercariae tended to concentrate the label in the foot, the mantle and the digestive gland. Little or no radioactivity was present in the areas where F. hepatica larvae were not found.

Animals↗

PubMed1990

The susceptibility of Lymnaeid snails to Paramphistomum cervi infections in Mexico.

The occurrence of Paramphistomum cervi has been reported in Mexico, but its intermediate hosts have not been identified. Five species of snails of the genus Lymnaea, L. bulimoides, L. columella, L. cubensis, L. humilis and L. palustris, were collected in Mexico. Only three of the exposed species, L. palustris, L. cubensis and L. humilis, became infected with P. cervi. The first of these snail species was highly susceptible to infection and a higher number of the exposed snails shed cercariae. It is suggested that L, palustris may act as an important vector of P. cervi in Mexico.

Animals↗

PubMed1990

Sterols in the plasma and digestive gland-gonad complex of Biomphalaria glabrata snails, fed lettuce versus hen's egg yolk, as determined by GLC.

1. Gas-liquid chromatography studies were done on sterols in plasma and the digestive gland-gonad (DGG) complex of Biomphalaria glabrata snails fed lettuce vs hen's egg yolk. 2. The major sterols present in the DGG of both populations were cholesterol, stigmasterol, beta-sitosterol, campesterol, and desmosterol. 3. The percentage composition of cholesterol in the DGG of yolk vs lettuce fed snails was 82 and 51, respectively. 4. The elution profiles of sterols in the plasma of yolk vs lettuce fed snails were similar; both contained desmosterol, campesterol, and stigmasterol, negligible amounts of cholesterol, and unidentified sterols. 5. The high lipid diet increased the level of cholesterol in the DGG but not in the plasma.

Animals↗

PubMed1985

The carboxylic and amino acid chemoreception niche of Bulinus rohlfsi (Clessin), the snail host of Schistosoma haematobium.

The response of the freshwater snail, Bulinus rohlfsi, to gradients of carboxylic acids, amino acids and some related compounds was investigated by means of diffusion olfactometers. The snails proved to be very discriminating in their responses to the chemical species tested and there were also very marked ontogenetic differences. Although 15 distinctive types of amino and carboxylic acids proved to be attractants and arrestants, only octanoic acid proved effective for snails of all ages. Possible mechanisms involved in the chemoreception of active compounds, the ecological, physiological and biochemical relevance of the responses and possible application to controlled release technology are discussed.

Amino Acids↗

PubMed2004

Toxic effects of cypermethrin and alphamethrin on reproduction and oxidative metabolism of the freshwater snail, Lymnaea acuminata.

Effects of sublethal exposure to cypermethrin and alphamethrin on the reproductive physiology and oxidative metabolism of the freshwater snail, Lymnaea acuminata, were studied. Sublethal exposure to both pyrethroids caused increases in the numbers of egg masses and eggs at all concentrations, but the survival rate of the snails was significantly reduced 28 days after of hatching. Both pyrethroids altered the oxidative metabolism in hepatopancreas and ovotestis tissues of the snails. Stress conditions result in less availability of oxygen and in turn less ATP production in tissues, adversely affecting oxidative metabolism and reproduction in L. acuminata.

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

Schistosomiasis models with density dependence and age of infection in snail dynamics.

New models for schistosomiasis are developed. These models incorporate several realistic features including drug treatment for human hosts, an infection age in snail hosts, density-dependent birth rate of snails, distribution of schistosomes within human hosts, and disease-induced mortality in both human and snail hosts. The qualitative and quantitative mathematical properties of the models are studied, their biological consequences and some control strategies are discussed, and the results of the new models are compared with those of simpler models. It is shown that the new model may have a bifurcation at which the unique endemic equilibrium changes the stability and stable periodic solutions exist. This is quite different from the simpler models. Explicit thresholds of treatment rate are established above which the infection will be controlled under certain levels. Evaluations of cost-effectiveness are also discussed by analyzing the sensitivity of the mean number of parasites per person to changes of other parameters.

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↗

PubMed1997

Bioaccumulation of aluminium in the freshwater snail Lymnaea stagnalis at neutral pH.

This study examined the accumulation of aluminium (Al) by the freshwater snail Lymnaea stagnalis at neutral pH, when most Al would be predicted to be in an insoluble form (Al(OH)(3)). Snails were exposed to a range of Al concentrations (38-285 microg l(-1)) for 30 days, followed by 20 days in clean water. Aluminium was measured using atomic absorption spectroscopy. Significant accumulation of Al occurred in the whole soft tissues, gut, digestive gland and kidney at the latest by day 10. High concentration factors were observed, ranging from 4.5 x 10(3) in the whole soft tissues to 6.3 x 10(4) in the kidney, corresponding to actual concentrations of 800 to 7500 microg g(-1), respectively. Proportionality between environmental (water) and tissue concentrations of Al was observed in the gut but not in the other tissues. Following transfer to clean water, rapid loss of Al from the whole soft tissues and gut was seen over the first 10 days. Loss of Al from the digestive gland was much less as a proportion of the total, with approximately 90% of the Al remaining in the tissue. In contrast, significant loss of Al from the kidney occurred between days 20 and 30, even in the continued presence of Al; little further loss occurred following transfer to clean water. Aluminium is clearly available to the snail at neutral pH, the most likely route of entry being the gut. This could facilitate entry of the metal into the food chain. The possible roles of the digestive gland and kidney in the handling of Al are discussed.

Journal Article↗