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PubMed1994

FMRFamide-related peptides from the kidney of the snail, Helisoma trivolvis.

Three FMRFamide-related peptides (FaRPs) were purified and characterized from the kidney of the snail, Helisoma trivolvis, by HPLC and detected using two radioimmunoassays (RIA) for FaRPs. Automated sequencing and mass spectrometry of the isolated peptides suggest the following sequences: Phe-Met-Arg-Phe-NH2 (FMRFamide), Phe-Leu-Arg-Phe-NH2 (FMRFamide), and Gly-Asp-Pro-Phe-Leu-Arg-Phe-NH2 (GDPFLRFamide). The FaRPs, predominantly the heptapeptides, were also detected by HPLC and RIA in other osmoregulatory tissues such as the skin, mantle, and the hemolymph. The level of FaRPs, detected by radioimmunoassay, appears to be lower in snails kept under hyposmotic stress than in snails kept under isosmotic stress. The FaRPs appear to be involved in osmoregulation in H. trivolvis.

Amino Acid Sequence↗

PubMed1995

Structural and biosynthetic properties of peptides in cone snail venoms.

Venoms of the predatory cone snails Conus textile, Conus striatus, and Conus magus were subjected to comprehensive analysis of peptide content. With the fish-eating cone snails C. magus and C. striatus, the most abundant venom peptides were of > 30-50 residues, whereas the predominant peptides in the venom of the mollusc-eating snail, C. textile, were of 20-35 residues. Amino acid sequencing revealed an identical but unusual amino acid in a conserved position in four novel omega-type peptides from the C. textile venom. Two conserved amino acid sequences were obtained from the venoms of both C. magus and C. striatus. The amino acid compositions of the isolated C. textile peptides and the expected processing products of the propeptides (42) were compared. Despite the recovery in abundance of the carboxyl-terminal omega-type peptides, none of the isolated peptides had compositions expected from the propeptide amino-terminal fragments. We conclude that there are likely mechanisms for excluding the amino-terminal propeptide fragments from this venom, resulting in a venom with greater potency. Amounts of the different omega-type peptides in the venom vary widely, suggesting a distinct mechanism that results in the selective synthesis of different bioactive carboxyl-terminal propeptide fragments at elevated levels.

Amino Acid Sequence↗

PubMed1977

Glycogen metabolism in the snail, Biomphalaria glabrata.

1. The distribution of glycogen in different tissues of the snail, Biomphalaria glabrata was determined; the cephalopedal region contained 15-17 mg, the mantle region 23-29 mg, the hepatopancreas 31-45 mg, and the ovotestis 50 mg of glycogen/g wet wt. 2. There was a significant decrease in the glycogen content in the cephalopedal region after incubating the snails with 5-hydroxytryptamine (4 x 10(-5) M) in vivo. 3. Enzymatic degradation of glycogen from different tissues revealed that the degree of branching was 9% of the total glucosyl residues, and the length of outer branches was about 40% of the total glucosyl residues. 4. There was an active form of glycogen phosphorylase in the cephalopedal region and the mantle region. Phosphorylase in the hepatopancreas was generally inactive, but could be activated by an endogenous phosphorylase kinase. 5. Glycogen synthetase of the snail tissues required glucose-6-phosphate to be active.

Animals↗

PubMed1984

The phase relationship of glycogen and free fatty acids in tissues of aestivating giant African snails (Achatina achatina).

The phase relationships of glycogen and free fatty acids (FFA) in the digestive (midgut) gland, foot muscle and heart muscle of starved and aestivating giant African snails (Achatina achatina) were analysed by means of phase plane plots. Phase plane plots of glycogen against FFA content indicated that these metabolites were out of phase in the digestive gland but in phase in the foot muscle, whereas the plot for the heart muscle had a long axis parallel to the abscissa. Digestive gland glycogen was out of phase with foot muscle FFA and with heart muscle FFA. Phase plane plots of foot muscle glycogen digestive gland FFA had its long axis parallel to the abscissa, whereas the plot of foot muscle glycogen against heart muscle FFA showed that these metabolites were in phase. Heart muscle FFA was in phase with either foot muscle FFA or digestive gland FFA. Pyruvate kinase extracted from the foot muscle of starved and aestivating snails was very labile and behaved like the allosteric type by exhibiting co-operative interaction with respect to phosphoenolpyruvate, allosteric activation by fructose 1,6-diphosphate and inhibition by ATP. The oscillatory motions of glycogen and FFA are discussed in terms of anaerobic metabolism in aestivating snails.

Anaerobiosis↗

PubMed1989

Intracellular mechanism of neurotransmitter-induced modulations of voltage-dependent Ca current in snail neurons.

This paper reviews our work on the modulation of voltage-dependent Ca currents in identified snail neurons. Ca currents of snail neurones are enhanced or decreased by neurotransmitters. Serotonin and acetylcholine enhance the Ca current of identified neurons, the effect of serotonin being mediated by cGMP and cGMP-dependent protein kinase. Cholecystokinin (CCK8) and dopamine both decrease the Ca current of identified neurons. The effect of CCK8 is irreversible and involves the activation of protein kinase C. The dopamine-induced decrease in Ca current is reversible and involves an alpha 40 subunit of a snail G protein immunologically and functionally related to alpha o of mammalian brain.

Animals↗

PubMed1992

Effects of adenine nucleosides and nucleotides on the isolated heart of the snail Helix aspersa and the slug Arion ater.

1. Adenine nucleosides and nucleotides were examined for pharmacological activity in hearts isolated from the snail Helix aspersa and the slug Arion ater. 2. Adenosine, AMP, ADP and ATP (above 100 microM) produced either an excitation or an inhibition in the isolated hearts of the snail and slug. 3. 2-Chloroadenosine, alpha, beta-methylene ATP and 2-methylthio ATP were inactive at concentrations up to 1 mM. 4. Responses were not blocked by any commonly accepted vertebrate purinoceptor antagonists, indicating that these purinoceptors are dissimilar to vertebrate purinoceptors and cannot be classified according to accepted purinoceptor classifications. 5. Electrical field stimulation of the snail heart produced frequency-dependent responses: 1-4 Hz produced predominantly excitation, 8-32 Hz predominantly inhibition. These responses were unaffected by the purines up 3 mM.

Adenine Nucleotides↗

PubMed1988

An alpha 40 subunit of a GTP-binding protein immunologically related to Go mediates a dopamine-induced decrease of Ca2+ current in snail neurons.

Dopamine induces a decrease in voltage-dependent Ca2+ current in identified neurons of the snail H. aspersa. This effect is blocked by intracellular injection of activated B. pertussis toxin and of an affinity-purified antibody against the alpha subunit of bovine Go protein. The dopamine effect is mimicked by intracellular injection of mammalian alpha o. In snail nervous tissue, pertussis toxin ADP-ribosylates a single protein band on SDS gels, and this band is recognized in immunoblots by the anti-alpha o antibody. We propose that this is a 40 kd alpha subunit of a molluscan G protein immunologically related to alpha o and that it mediates the effect of dopamine on Ca2+ currents in identified snail neurons.

Animals↗

PubMed2006

G-protein coupled receptor kinase-like immunoreactivity in the snail, Helix pomatia, neurons.

GPRCs are regulated via phosphorylation by different protein kinases including GRKs and PKA and PKC. The purpose of this study was to determine the presence and physiological role of GRKs in the tissues of the snail, Helix pomatia. Here we report that immunoblotting of brain homogenate with anti-GRK2/3 antibody prepared from mammalian tissue can be detected in snail GRK-like immunoreactivity. The GRK2/3 immunoreactivity was found at approximately 80 kDa in a variety of cells, including salivary duct, salivary gland and eye. Intracellular injection of the anti-GRK2/3 prevented the neuron from desensitization and agonist-induced activation augmented the phosphorylated GRKs in the membrane fraction suggesting that GRKs may have a functional role in the neuropeptide receptor desensitization in snail.

Animals↗

PubMed2006

Permeability of the haemolymph-neural interface in the terrestrial snail Megalobulimus abbreviatus (Gastropoda, Pulmonata): an ultrastructural approach.

The aim of this study was to investigate the ultrastructure of the interface zone between the nervous tissue and the connective vascular sheath that surround the central ganglia of the terrestrial snail of Megalobulimus abbreviatus and test its permeability using lanthanum as an electron dense tracer. To this purpose, ganglia from a group of snails were fixed by immersion in a 2% colloidal lanthanum solution, and a second group of animals was injected in the foot with either a 2%, 10% or 20% lanthanum nitrate solution and then sacrificed 2 or 24 h after injection. Ganglia from both groups were processed for transmission electron microscopy. The vascular endothelium, connective tissue and basal lamina of variable thickness that ensheathe the nervous tissue and glial cells of the nervous tissue constitute the interface zone between the haemolymph and the neurones. The injected lanthanum reached the connective tissue of the perineural capsule; however, it did not permeate into the nervous tissue because the basal lamina interposed between both tissues interrupted this passage. Moreover, the ganglia fixed with colloidal lanthanum showed electron dense precipitates between the glial processes in the area adjacent to the basal lamina. It can be concluded from these findings that, of the different components of the haemolymph-neuronal interface, only the basal lamina, between the perineural capsule and the nervous tissue, limits the traffic of substances to and from the central nervous system of this snail.

Animals↗

PubMed2004

Acute toxicity of cadmium and copper in hepatopancreas cells from the Roman snail (Helix pomatia).

The toxic effects of cadmium (Cd) and copper (Cu) on cellular metabolism and cell morphology were investigated in isolated hepatopancreas cells from the Roman snail (Helix pomatia). Cell viability was unaffected during 1 h of incubation with 100 microM Cd, but was significantly reduced from 93% in controls to 87% and 85% with 100 microM Cu and 500 microM Cd, respectively. The adverse effect of 500 microM Cd on cell viability was not observed in cells isolated from Cd pretreated snails. Oxygen consumption remained constant in the presence of 100 microM Cu but was inhibited by 38% after 1 h of exposure to 500 microM Cd. Hepatopancreas cells showed enhanced formation of reactive oxygen species when exposed to 100 microM Cu, but not in the presence of Cd. Morphologically, an increase in cell volume of Cd-exposed cells was noted, while cell membrane bleb formation was induced by both metals. The latter may have been induced by metal effects on the actin filamentous network of the cells which showed distinct actin-staining within the blebs at the cell surface. Overall, our data indicate that both Cd and Cu are acutely toxic for hepatopancreas cells form the Roman snail with Cu being more toxic than Cd.

Animals↗

PubMed2006

An invertebrate embryo test with the apple snail Marisa cornuarietis to assess effects of potential developmental and endocrine disruptors.

A novel invertebrate embryo test with the apple snail, Marisa cornuarietis, comprising a test protocol for the following developmental endpoints is described: formation of eyes and tentacles, heart rate, hatching, weight after hatching. To evaluate effects on embryonic development, the snails were treated in a first step with 250 or 500 microg/l cadmium. Sublethal effects in terms of a significant delay in hatching could be found in the 250 microg/l treated animals, whereas 500 microg/l Cd were lethal for the snail embryos. To test endocrine disrupting chemicals with this protocol, experiments with bisphenol A (50 microg/l, 100 microg/l) and 17alpha-ethinylestradiol (10 microg/l) were performed. In both treatments an increase of weight after hatching was observed as well as a significant decline in the heart rate of the embryos. As shown here, the sensitivity of M. cornuarietis embryos test is equal or even higher than other test species like zebrafish embryos and, therefore, this test can be regarded as an alternative or supplement for ecotoxicological studies.

Animals↗

PubMed2006

Dorsal-ventral pattern of Delta trafficking is established by a Snail-Tom-Neuralized pathway.

The intracellular trafficking of the Notch ligand Delta plays an important role in the activation of the Notch pathway. We have addressed the snail-dependent regulation of Delta trafficking during the plasma membrane growth of the mesoderm in the Drosophila embryo. We show that Delta is retained in endocytic vesicles in the mesoderm but expressed on the surface of the adjacent ectoderm. This trafficking pattern requires Neuralized. We developed a protocol based on chromosomal deletion and microarray analysis that led to the identification of tom as the target of snail regulating Delta trafficking. Snail represses Tom expression in the mesoderm and thereby activates Delta trafficking. Overexpression of Tom abolishes Delta trafficking and signaling to the adjacent mesoectoderm. Loss of Tom produces mesoderm-type Delta trafficking in the entire blastoderm epithelium and an expansion of mesoectoderm gene expression. We propose that Tom antagonizes the activity of Neuralized and thus establishes a sharp mesoderm-mesoectoderm boundary of Notch signaling.

Animals↗

PubMed2005

Quantitative changes in the digestive gland cells of the snail Helix aspersa after exposure to the fungicide copper oxychloride.

This study investigated the relationship between accumulated copper in the digestive gland of Helix aspersa, after exposure to the fungicide copper oxychloride, and quantitative changes in the digestive gland cells of this snail. Snails were exposed to 80 and 240 microg g(-1) copper oxychloride for 6 weeks. Histological sections of digestive glands were analyzed by means of computer-assisted image analysis. Results indicate that copper is strongly accumulated in the digestive gland and that this organ is the main site of copper accumulation in the snail body. Also, as a result of copper accumulation in the digestive gland, measurable changes in epithelium cell height and area of this organ occur. In the case of cell height, these changes are dose-related. It is concluded that changes in digestive gland cells, as a result of copper oxychloride exposure, may possibly serve as biomarkers of exposure to this fungicide.

Animals↗

PubMed2004

Role of exogenous and endogenous silicon in ameliorating behavioural responses to aluminium in a freshwater snail.

Aluminium accumulation by the freshwater snail Lymnaea stagnalis is correlated with behavioural depression which is ameliorated by addition of orthosilicic acid. We hypothesised that Si is relocated to the digestive gland in response to Al, leading to the formation of non-toxic hydroxyaluminosilicates (HAS). Exposure to 500 microg l(-1) Al for 30 days was associated with an initial period of behavioural depression, followed by apparent tolerance and subsequent depression, suggesting saturation of the cellular detoxification pathway during prolonged exposure. Exogenous Si (7.77 mg l(-1)) completely ameliorated all behavioural effects of Al but did not prevent its accumulation. In the presence of added Al, significantly more of this Si was accumulated by the tissues, compared to controls and snails exposed to Si alone. In snails exposed to Al plus Si, Al and Si concentrations were significantly correlated, with a ratio around 3:1 Al:Si, consistent with the presence of the non-toxic HAS protoimogolite.

Aluminum↗

PubMed2006

Pathological reactions and recovery of hepatopancreatic digestive cells from the marine snail Littorina littorea following exposure to a polycyclic aromatic hydrocarbon.

The aim of this study was to investigate the cellular pathological responses of hepatopancreatic digestive cells from the periwinkle Littorina littorea exposed to the polycyclic aromatic hydrocarbon (PAH) fluoranthene and to ascertain whether any injurious effects were reversible within the experimental time scale. A secondary objective was to establish the relationship of the various reactions to animal health status, using lysosomal stability as an index of well-being. Exposure of snails to a concentration of 335 microgl(-1) (1.7 microM) fluoranthene (seawater renewed and spiked daily with fluoranthene) for 5 days resulted in a reduction in lysosomal stability (neutral red retention) and endocytosis; and an increase in smooth endoplasmic reticulum (ER) and 7-ethoxycoumarin-o-deethylase (ECOD; measured as cyano-ECOD) activity measured in isolated live digestive cells. Exposed snails treated with clean seawater for a further 8 days resulted in a return to control levels of lysosomal stability, ECOD and ER; endocytosis showed only a partial recovery. Multi-variate and uni-variate analysis showed that there were strong correlations between the various cellular biomarker responses. These findings are interpretable within the current framework of molluscan biomarker responses to PAHs. Principal component analysis was used to derive the first principal component for endocytosis, ER and ECOD reactions and these were plotted against lysosomal stability as a measure of cellular well-being. The resulting significant regression represents the mapping of the individual biomarkers within health status space for a gradient of fluoranthene toxicity. From this analysis, we concluded that endocytosis is an indicator of healthy snails while proliferation of ER and to a lesser extent induced ECOD are indicative of dysfunction and reduced health. Finally, the results indicate that stress induced by chronic exposure to a PAH is reversible.

7-Alkoxycoumarin O-Dealkylase↗

PubMed2006

Associations between shell strength, shell morphology and heavy metals in the land snail Cepaea nemoralis (Gastropoda, Helicidae).

In snails there is an intimate relation between shell size, thickness, strength and calcium content that may be influenced by environmental factors such as predation and heavy metal pollution. The snail Cepaea nemoralis shows variability for shell colour and banding pattern, and frequencies of colour morphs are highly variable in natural populations. We used C. nemoralis to investigate (i) the relations between shell morphology, shell Ca and heavy metal content (Cd, Cr, Pb, Zn), and shell strength, (ii) differences in shell morphology and shell strength among localities and yellow and pink shells and (iii) whether snails from polluted sites show increased levels of heavy metals in their shell. Larger shells were heavier, thicker, needed a higher force to be crushed but did not have a higher Ca concentration. Cd and Zn concentrations were higher in shells from polluted plots compared to shells from unpolluted plots but Ca levels in the shell were comparable among plots. Zn concentration was negatively correlated with shell traits. Although there was substantial variation in shell strength, thickness and dry weight among localities, none of the shell traits differed between individuals from polluted and reference plots nor between colour morphs. Our results suggest that the effect of heavy metal pollution on shell strength and morphology is limited in the investigated populations.

Animals↗

PubMed2006

Accumulation of microcystins in various organs of the freshwater snail Sinotaia histrica and three fishes in a temperate lake, the eutrophic Lake Suwa, Japan.

So far, there has been only one study to examine microcystin (MC) contents in various organs of snails in a subtropical Chinese lake. In this study, tissue distribution and seasonal dynamics of MC-RR and -LR were investigated in various organs of a freshwater snail (Sinotaia histrica) in a temperate eutrophic lake, Lake Suwa, Japan. Accumulation of microcystins in some fish was also investigated. There was marked temporal variation in the MC content of various organs of the snail. The digestive tract had the highest MC content (mean 9.03 microg g(-1) DW and range 3.74-23.2 microg g(-1) DW), followed by the gonad (mean 6.90 microg g(-1) DW and range 0.07-22.7 microg g(-1) DW) and hepatopancreas (mean 5.38 microg g(-1) DW and range 1.08-8.79 microg g(-1) DW), whereas the foot had the least (mean 2.48 microg g(-1) DW and range 0.04-4.45 microg g(-1) DW). The disappearance of MC-LR in the hepatopancreas indicated that S. histrica is able to depurate MC-LR efficiently. MC-RR was detected in the muscle of three species of fish, with the highest content in Carassius auratus (79.4 microg kg(-1) BW). Because of substantial MC accumulation in these edible aquatic animals in Lake Suwa, it is recommended that regular monitoring of MCs should be undertaken in both cyanobacteria and aquatic animals.

Animals↗

PubMed2003

Hypoxia attenuates the expression of E-cadherin via up-regulation of SNAIL in ovarian carcinoma cells.

Since ovarian carcinoma cells detach from the primary lesion and metastasize via peritoneal dissemination, we hypothesized that these cells are exposed to hypoxia, which may affect cell attachment and invasiveness. To address this hypothesis, we first examined in vivo the immunohistochemical expression of hypoxia-inducible factor-1alpha (HIF-1alpha) and its topological correlation with E-cadherin expression in ovarian carcinomas. We then examined in vitro the effect of hypoxia on the mRNA and protein expressions of E-cadherin using two ovarian cancer cell lines, SKOV3 and OVCAR3, and normal ovarian surface epithelial (OSE) cells. In addition, hypoxia-induced change in the expression of SNAIL, a transcriptional factor repressing E-cadherin expression, was also analyzed. Finally, we examined the facilitation of invasiveness of ovarian cancer cells under hypoxia using Matrigel invasion assay. Immunohistochemically, nuclear localization of HIF-1alpha was observed in 32 of the 76 (42%) carcinomas studied, and showed a topological correlation with loss of E-cadherin expression. Northern blotting, real-time PCR and Western blotting demonstrated that E-cadherin expression was remarkably decreased under hypoxia in both SKOV3 and OVCAR3 cells, but not in normal OSE cells. mRNA expression of SNAIL was increased under hypoxia in both ovarian cancer cell lines. Invasion assay revealed that hypoxia increases the invasiveness of ovarian cancer cells. Accordingly, the present study demonstrated that hypoxia induces down-regulation of E-cadherin in ovarian carcinoma cells, via up-regulation of the transcriptional repressor SNAIL. These findings suggest that hypoxia plays an important role in the change in intercellular attachment, which may be involved in the initiation of tumor progression of ovarian cancer cells.

Cadherins↗