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At least 1,117 records · Page 62Linked to original sources
PubMed2003

Sodium channel modulating activity in a delta-conotoxin from an Indian marine snail.

A 26 residue peptide (Am 2766) with the sequence CKQAGESCDIFSQNCCVG-TCAFICIE-NH(2) has been isolated and purified from the venom of the molluscivorous snail, Conus amadis, collected off the southeastern coast of India. Chemical modification and mass spectrometric studies establish that Am 2766 has three disulfide bridges. C-terminal amidation has been demonstrated by mass measurements on the C-terminal fragments obtained by proteolysis. Sequence alignments establish that Am 2766 belongs to the delta-conotoxin family. Am 2766 inhibits the decay of the sodium current in brain rNav1.2a voltage-gated Na(+) channel, stably expressed in Chinese hamster ovary cells. Unlike delta-conotoxins have previously been isolated from molluscivorous snails, Am 2766 inhibits inactivation of mammalian sodium channels.

Amino Acid Sequence↗
PubMed1998

Single-species infections of Echinostoma caproni cercariae in pulmonate snails and concurrent infections of E. caproni and Echinostoma trivolvis cercariae in Biomphalaria glabrata.

Single-species infections of Echinostoma caproni cercariae in various pulmonate snails showed that a higher percentage of cercariae encysted successfully in Biomphalaria glabrata than in other snail species and that the percentage encystment was significantly greater in B. glabrata than in either Helisoma trivolvis or Lymnaea elodes. There were significant differences in cyst diameter, thickness of outer and inner cysts, and diameter of excretory concretions between E. caproni and Echinostoma trivolvis metacercariae. These morphological differences helped to distinguish each species of cyst in concurrent cercarial infections of E. caproni and E. trivolvis in B. glabrata. Moreover, in concurrent infections E. trivolvis localised only in the saccular kidney, whereas E. caproni occurred in both the saccular kidney and the pericardium.

Animals↗
PubMed2003

Culturing neurons from the snail Helisoma.

The large neurons of the freshwater snail Helisoma trivolvis provide a unique preparation to study cytoskeletal mechanisms involved in neuronal growth and axon guidance. When placed into culture, these neurons form large growth cones in which cytoskeletal components and their dynamics can be analyzed with high-spatial resolution. Moreover, these growth cones display all of the dynamic features characteristic of growing axons, including advance, pause, collapse, and turning, allowing the correlation of cell biological mechanisms with growth cone motility. This chapter describes complete procedures for culturing Helisoma neurons, including snail dissection, enzymatic treatments, removal of neurons, and necessary solutions, equipment, and supplies. Techniques are presented to culture Helisoma neurons by the extraction and transfer of individual neurons to culture dishes. A newer technique to dissociate neurons from whole ganglia is also described. In addition, methods to culture neurons on two substrates are presented. Culturing on polylysine in defined medium produces large, but nonmotile growth cones for cytoskeletal analysis, whereas culturing on polylysine in conditioned medium allows growth and motility for behavioral analysis. Recent tests suggest a new, simpler formulation for the medium used to culture Helisoma neurons that does not require the special-order medium that was previously used for cultures. These procedures make it feasible for someone inexperienced to successfully culture Helisoma neurons for use in a variety of experiments.

Animals↗
PubMed2000

Fulicin regulates the female reproductive organs of the snail, Achatina fulica.

Fulicin is a D-amino acid-containing neuropeptide that has been thought to control male copulatory behavior in the land snail, Achatina fulica. In the present study, we demonstrated that the vagina and the oviduct of Achatina were densely innervated by fulicin-like immunoreactive neuronal fibers. We confirmed that fulicin was actually present in the vagina by mass spectrometry. Furthermore, fulicin showed a profound excitatory effect on contractions of the vagina and the oviduct. These results suggest that fulicin controls female egg-laying behavior as an excitatory neuropeptide regulating the female reproductive organs of the snail.

Animals↗
PubMed2000

The neuropeptide APGWamide induces imposex in the mud snail, Ilyanassa obsoleta.

We investigated whether neuropeptides which control sexual differentiation in mollusks can induce imposex-a condition where female snails grow male accessory sex organs after exposure to tributyltin (TBT). Mud snails, Ilyanassa obsoleta, were dosed with one of four neuropeptides: APGWamide, conopressin, LSSFVRIamide, or FMRFamide for seven or fourteen days. TBT and testosterone (T) were used as positive controls and induced imposex as expected. APGWamide significantly induced imposex, with a threshold dose near 10(-)(16) moles. The other neuropeptides had no effect on imposex induction. We propose that TBT could act as a neurotoxin to induce imposex via abnormal release of APGWamide.

Animals↗
PubMed1997

Characterization of myomodulin-related peptides from the pulmonate snail Helix aspersa.

Three myomodulin-related peptides--pQLSMLRLamide, PMSMLRLamide, and SLGMLRLamide--have been purified and sequenced from extracts of whole snails. The level of immunoreactive myomodulin was shown by HPLC and RIA to be widely distributed among 26 different snail tissues, with the highest levels (higher even than those in the central ganglia) occurring in certain male reproductive organs. Synthetic pQLSMLRLamide modified either the spontaneous rhythmic activity or the resting tone of several isolated muscular organs: the aorta, ventricle, upper gut, epiphallus, flagellum, and spermatheca; but the retractor muscles of the pharynx, penis, and tentacle were unaffected.

Animals↗
PubMed2002

Lead reduces shell mass in juvenile garden snails (Helix aspersa).

In an earlier paper examining inherited tolerance to Pb, the shell growth of laboratory-bred offspring of Helix aspersa from contaminated sites was compared with that ofjuveniles from naive populations on dosed and undosed diets. Eight-week-old snails were fed either 500 microg g(-1) Pb or a control food in competitive trials between two populations. In the first series of trials, a parental history of exposure to Pb did not confer any advantage to either of two populations (BI and MI) competing with a naïve population (LE). whether Pb was present in the diet or not. However, in the analysis of their metal concentrations reported here, LE are found to retain higher levels of Pb in the soft tissues than either BI or MI. Compared to their siblings on the unleaded diet, dosed LE and BI juveniles had lower soft tissue concentrations of Ca and Mg. Although the growth in shell height is unaffected by diet, LE and BI juveniles build lighter shells on the Pb-dosed diet, achieving around 75% of the shell mass of their controls. In contrast, the shell weights of dosed MI juveniles are depressed by only 15% and show no change in the essential metal concentrations of their soft tissues. A second experiment using five populations fed only the dosed food show that the shell weight/soft tissue weight ratios are comparable to the dosed snails of the previous experiment. Building a lighter shell thus appears to be the common response of all Helix populations to a high Pb diet, at least amongst juveniles. The reduction in its mass means that less Ca and Mg is added to the shell and, along with the lowered soft tissue concentrations observed in some populations. may be a consequence of an increased effort to excrete Pb. The possibility that the MI population shows a genotypic adaptation. perhaps as some form of modification of its Ca metabolism, is briefly discussed.

Adaptation, Physiological↗
PubMed1999

Effects of l-amphetamine on the central neurons of the snail.

The effects of l-amphetamine on the spontaneous firing of central neurons of African snails (Achatina fulica Ferussac) were studied electrophysiologically. The effects of dopamine, noradrenaline, d-amphetamine, and methamphetamine on the central neurons also were tested. The l- and d-amphetamines (0.3 mM) elicited bursting firing of action potentials in the RP4 neuron of the snail, whereas dopamine (0.3 mM), noradrenaline (NE, 0.3 mM), and methamphetamine (2 mM) did not. The bursting firing of action potentials elicited by l-amphetamine was decreased if potassium-free solution, sodium-free solution, or solution containing oubain (0.1 mM), a sodium pump inhibitor, was perfused. The results suggested that l-amphetamine did, and methamphetamine did not, elicit a sodium-dependent bursting firing of action potentials of the neuron.

Action Potentials↗
PubMed1998

Putative neuropeptides and an EF-hand motif region are encoded by a novel gene expressed in the four giant interneurons of the terrestrial snail.

Nine giant interneurons located in the pleural and parietal ganglia of the terrestrial snail Helix lucorum L. were reported to be a key element in the network controlling withdrawal behaviour of the animal. Using a combination of complementary DNA subtraction cloning and differential screening approaches we have isolated a novel gene named HCS2 which is expressed predominantly in a subset of these interneurons. The predicted amino acid sequence of the HCS2 protein contains at the N-terminus a hydrophobic leader sequence and four putative neuropeptides, and at the C-terminus a perfect match to the consensus motif of the EF-hand family of the Ca2+-binding proteins. All four predicted neuropeptides bear a C-terminal signature sequence Tyr-Pro-Arg-X (where X is Ile, Leu, Val or Pro), and three of them are likely to be amidated. Physiological action of three synthetic peptides corresponding to the predicted mature HCS2 peptides mimics fairly well the described action of parietal interneurons on follower motoneurons controlling pneumostome closure. In situ hybridization experiments demonstrated that the HCS2 gene is selectively expressed in the four parietal giant interneurons, as well as in several small unidentified neurons. The onset of the HCS2 transcription during embryogenesis coincides temporally with the time-point when the first withdrawal responses of the embryo to tactile stimulation appear. We propose that the HCS2 gene encodes a hybrid precursor protein whose processed products act as neuromodulators or neurotransmitters mediating the withdrawal reactions of the snail, and in addition may participate in the calcium regulatory pathways or calcium homeostasis in command neurons.

Amino Acid Sequence↗
PubMed2001

Poaceae in the natural diet of the snail Helix aspersa Müller (Gastropoda, Pulmonata).

The natural diet of Helix aspersa was studied in two populations by analysing faeces. Picris echioides, Carduus tenuifloris, Urtica dioica, Galium molugo (Dicotyledons) and Poaceae (Monocotyledons) were the principal resources of the studied populations. The species of Poaceae ingested by Helix aspersa in July were determined by analysing the phytoliths present in the faeces. Festuca rubra, Dactylis glomerata and Bromus hordeaceus seemed to be attractive for the snails whereas Elytrigia repens was rejected. These results were convergent with the ingestion rates of Poaceae in the laboratory but assimilation efficiencies did not explain these choices. Poaceae with the highest energetic values were not preferred to others. The texture, the mineral and organic contents of the Poaceae may be responsible for the snails feeding choices. The importance of Poaceae for this species is discussed.

Animals↗
PubMed1999

Biological control and invading freshwater snails. A case study.

Introductions of four species of freshwater snails occurred between 1972 and 1996 onto Guadeloupe Island. Two of them, Melanoides tuberculata and Marisa cornuarietis, were subsequently used as biological control agents against Biomphalaria glabrata, the snail intermediate host of intestinal schistosomiasis. In 1996, a general survey was carried out in 134 sites which had already been investigated in 1972. The total number of mollusc species had increased from 19 to 21. Site numbers housing B. glabrata and two other species had strongly declined. This decline may be mainly attributed to a competitive displacement by M. tuberculata and M. cornuarietis as illustrated by several biological control programmes. There were no changes in the remainder of the malacological fauna.

Animals↗
PubMed1998

Functional determinants by which snake and cone snail toxins block the alpha 7 neuronal nicotinic acetylcholine receptors.

Snakes and cone snails produce toxins which block muscular and/or neuronal nicotinic acetylcholine receptors (AChRs). This paper mostly focuses on the determinants by which a snake long chain curaremimetic toxin and the cone snail toxin ImI bind specifically to the alpha 7 neuronal receptor. In both cases, the site involves a small turn-like structure constrained by two half-cystines.

Amino Acid Sequence↗
PubMed2002

Cell movements during gastrulation: snail dependent and independent pathways.

The morphogenetic process of gastrulation requires multiple inputs and intricate coordination. Genetic analyses demonstrate critical roles of vertebrate and invertebrate Snail proteins in this process. Together with other regulatory molecules including Wnt and BMP, the Snail pathways specify cell fate and reorganize cellular machineries to coordinate morphological changes and cell movements during gastrulation.

Adherens Junctions↗
PubMed2004

The Pleistocene glaciations and the evolutionary history of the polytypic snail species Arianta arbustorum (Gastropoda, Pulmonata, Helicidae).

The evolutionary history of the snail Arianta arbustorum is controversial. This diverse, polytypic species has two distinct forms: one, with a globular shell and closed umbilicus, is found from lowland to high altitudes; the other, with a depressed shell and open umbilicus, is found at a few scattered, high altitude localities. What is the origin of these two forms? Some believe that the depressed shell is a recent, local, ecotypic adaptation to alpine environments. Others believe that this form is a relic of an ancestral condition that may have survived the Pleistocene glaciations on nunatak-like montane refugia, while the globular shell is a derived condition and its presence at high altitudes follows post-Pleistocene recolonisation. We analysed a portion of the mitochondrial gene cytochrome oxidase I for 100 snails of the species A. arbustorum, three additional Arianta species, and nine outgroup taxa from five genera, in order to understand the phylogeographic history of the species. Despite some confounding artefacts that are likely due to introgression among the morphological forms, the resulting phylogeny shows that the depressed shell is plesiomorphic, while the globular shell is derived. Moreover, their disparate histories suggest that the depressed shell variety survived the glaciations in pockets of alpine refugia, while the globular shell variety recolonised the alpine environment post-glacially.

Animals↗
PubMed2001

Some rare larval trematodes of prosobranch snails, Semisulcospira spp., in the Lake Biwa drainage system, central Japan.

A total of 17737 individuals of prosobranch snails, Semisulcospira spp., were collected from Lake Biwa and its tributaries, central Japan, from 1995 to 1999. They were examined for trematode larvae. One species of Aspidogastrea and 28 species of Digenea were detected. This paper briefly describes five of the 28 digeneans: a tetracotyle metacercaria from S. niponica, Cercaria A (cystophorous cercaria) from S. reticulata, Cercaria B (echinostomatid cercaria) from S. libertina, Cercaria C (magnacauda cercaria) from S. niponica and Cercaria D (mutabile cercarium) from S. nakasekoae. They were rare and every one of them was obtained from one snail only once.

Animals↗
PubMed2002

Serodiagnosis of human opisthorchiasis using cocktail and electroeluted Bithynia snail antigens.

Cocktail and electroeluted antigens from Bithynia goniomphalos, the snail intermediate host of Opisthorchis viverrini, were extracted and purified. The performance of these two antigens in the antibody detection of human opisthorchiasis was evaluated by indirect ELISA. Serum samples from people whose stool was either: (i). positive for Opisthorchis eggs (n=61); or (ii). positive for at least one of 19 other species of parasite (n=125); or (iii). clear of parasites (n=30) were tested. The sensitivity, specificity, positive predictive value and negative predictive value of ELISA using cocktail antigen were 88.5, 88, 78.2 and 94%, respectively; those of ELISA using eluted antigen (53 kDa) were 91.8, 98.4, 96.5 and 96.1%, respectively. Cross-reaction with the eluted antigen was seen in only one of four cases of hymenolepiasis and only one of 10 cases of strongyloidiasis. The kappa coefficients for ELISA in relation to stool examination were 0.84 (cocktail antigen) and 0.87 (eluted antigen). This study showed that Bithynia snail antigen could be used to replace worm antigen in the antibody detection of human O. viverrini infection.

Acrylic Resins↗
PubMed2003

Trematode fauna of prosobranch snails of the genus Semisulcospira in Lake Biwa and the connected drainage system.

The parasite fauna of prosobranch snails of the genus Semisulcospira was surveyed in Lake Biwa and the adjacent water system. One aspidogastrean and 28 digenetic trematode taxa were detected in 19209 snails consisting of 10 morphological species. There was no trematode species peculiar to members of the subgenus Biwamelania that is endemic to the Lake Biwa water system. However, one species, Notocotylus magniovatus, was found only in the non-endemic subgenus Semisulcospira. Of 23 digenean taxa detected in more than one host, 13 were distributed in both the lake and the tributaries. Seven of these had host taxa, more than 1% of which were infected with the parasite in both the lake and the tributaries, four had such hosts only in the tributaries, and two had no such hosts. Three species detected only in Lake Biwa were previously reported from other rivers in Japan. In the seven species detected only in the tributaries, two species had life cycles that could be maintained only in rivers. These results indicate that the core areas for the distribution of parasites of Semisulcospira are tributaries, and the lake is a sink for these species. These results contradict the expectation that the parasite fauna should be richer in the lake than in tributaries because the lake is a stable habitat over a geological time scale and has more divergent freshwater animals than the adjacent water system.

Animals↗
PubMed1987

Observations on the transmission of Angiostrongylus cantonensis from snail to rodent.

A survey of Angiostrongylus cantonensis was carried out to investigate the mode of transmission from mollusc to rat in a fixed study area of Yoron Island from 1979 to 1982. Rattus rattus was found to be infected with a small number of worms in spite of heavy infection with third-stage larvae in Achatina fulica and an abundance of this snail in the area. Natural infection and/or susceptibility with A. cantonensis were confirmed in three small snail species. Bradybaena circulus, Fruticicola despecta and Luchuena reticulata. Young A. fulica was found to be infected with fewer third-stage larvae than mature A. fulica. It was concluded that molluscs which were infected with a small number of third-stage larvae of A. cantonensis play an important role in maintaining the life cycle of A. cantonensis. The percentage of rat stomachs containing mollusc tissue was relatively low, and the incidence and infection was low in rats. Infection with A. cantonensis did not occur very often in R. rattus in nature.

Angiostrongylus↗