SEARCH · PubMed Health

Results for “Snails”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 397 records · Page 22Linked to original sources

PubMed1978

Effects of parasitism and stress on hemolymph protein of the African giant snail, Achatina fulica.

Effects of parasitism and stress on the protein concentration of hemolymph have been investigated using the rat lungworm Angiostromgylus cantonensis in the snail host Achatina fulica. The normal hemolymph protein concentration, averaging 1.77 g/100 ml in noninfected snails, did not show any reduction when the hosts were infected with third stage larvae. When the infected snails were bled repeatedly, protein concentration showed a significant decrease by 0.6 g/100 ml. Starved, infected snails were capable of maintaining their hemolymph protein level within the normal range. This treatment, however, in combination with frequent bleeding, caused much stress to the snails and reduced survival. The number of survivors depended on the frequency of bleeding and on the food level.

Animals↗

PubMedDate not supplied

Facilitation of defense reactions during the consumption of food in snails: the participation of glucose and gastrin/cholecystokinin-like peptide.

The molecular-cellular mechanisms of the interrelationships between the alimentary and defense behavior of snails were investigated. The clarity of manifestation of defense reactions at various stages of the satisfaction of alimentary need was studied. It was found that the defense reactions were attenuated in starved molluscs, whereas after a 20-minute feeding session the facilitation of generalized defense reactions takes place, the clarity of manifestation of which depends on the duration of food deprivation. It was demonstrated that an increase in the level of glucose in the hemolymph of the starved molluscs to the level present in the hemolymph during a meal (1.6-2.0 mM), as well as the administration of 20-30 ng of analogs of gastrointestinal peptides (pentagastrin or cholecystokinin octapeptide, CCK-8) elicits the facilitation of generalized defense reactions similar to that found during the feeding of the snails. The directionality of the changes in the activity of the L-RPl1 neurons during the application of carrot juice to the lip of semi-intact preparations of starved snails depended on the presence of glucose in the solution bathing the central nervous system. Similar glucose-dependant changes were found after the application of CCK-8 to the CNS of starved snails, but not of FMRFamide, whereas the isolated application of glucose did not exhibit such an effect. It was found that the L-RPl1 neurons were the most sensitive to the change in the concentration of glucose and CCK-8 in the perfusate. The adaptive significance of the dependance of the clarity of manifestation of defense reactions on the level of alimentary need of the snails and the participation of glucose and gastrin or cholecystokinin-like peptide in these processes are discussed.

Aggression↗

PubMedDate not supplied

Role of G-proteins and second messenger systems in the plasticity of a defensive reflex in the common snail.

Enzymatic methods were used to demonstrate an increase in the activity of G-proteins and protein kinase A in the brain of the common snail at early stages of learning. There were no differences in the activity of G-proteins in the brain between young (unable to learn) and adult snails. Snail brain protein kinase C activity was unchanged compared to controls 20-40 minutes after the end of the training procedure. It is concluded that cAMP-dependent phosphorylation and cAMP-dependent activation of early gene expression have active roles in learning in the snail. The question of the role of additional intracellular regulatory systems in learning in the snail is discussed.

Animals↗

PubMed2005

The convoluted evolution of snail chirality.

The direction that a snail (Mollusca: Gastropoda) coils, whether dextral (right-handed) or sinistral (left-handed), originates in early development but is most easily observed in the shell form of the adult. Here, we review recent progress in understanding snail chirality from genetic, developmental and ecological perspectives. In the few species that have been characterized, chirality is determined by a single genetic locus with delayed inheritance, which means that the genotype is expressed in the mother's offspring. Although research lags behind the studies of asymmetry in the mouse and nematode, attempts to isolate the loci involved in snail chirality have begun, with the final aim of understanding how the axis of left-right asymmetry is established. In nature, most snail taxa (>90%) are dextral, but sinistrality is known from mutant individuals, populations within dextral species, entirely sinistral species, genera and even families. Ordinarily, it is expected that strong frequency-dependent selection should act against the establishment of new chiral types because the chiral minority have difficulty finding a suitable mating partner (their genitalia are on the 'wrong' side). Mixed populations should therefore not persist. Intriguingly, however, a very few land snail species, notably the subgenus Amphidromus sensu stricto, not only appear to mate randomly between different chiral types, but also have a stable, within-population chiral dimorphism, which suggests the involvement of a balancing factor. At the other end of the spectrum, in many species, different chiral types are unable to mate and so could be reproductively isolated from one another. However, while empirical data, models and simulations have indicated that chiral reversal must sometimes occur, it is rarely likely to lead to so-called 'single-gene' speciation. Nevertheless, chiral reversal could still be a contributing factor to speciation (or to divergence after speciation) when reproductive character displacement is involved. Understanding the establishment of chirality, the preponderance of dextral species and the rare instances of stable dimorphism is an important target for future research. Since the genetics of chirality have been studied in only a few pulmonate species, we also urge that more taxa, especially those from the sea, should be investigated.

Animal Structures↗

PubMed2002

Indirect effects of heavy metals on parasites may cause shifts in snail species compositions.

We studied the direct and indirect effects of pollution on the distributions and abundances of two closely related species of pulmonate freshwater snails. Physella columbiana is more numerous at heavy metal-polluted lakes, and Lymnaea palustris is more numerous at reference lakes. Both species are present at all sites, as are predatory bluegill sunfish (Lepomis macrochirus). The direct effects examined included the snails' growth and reproduction in both the presence and absence of heavy metals and their short-term survival when exposed to large concentrations of heavy metals. The indirect effects were the species' ability to elude capture by sunfish and the diversity and abundance of parasites within the snails. We found that heavy metals had little direct effect on growth and reproduction and that both species acquired similar levels of metals in their tissues. Interestingly, P. columbiana (the more abundant species in polluted lakes) actually exhibited higher recruitment in the absence of metals than did L. palustris (reference lakes). L. palustris has life history characteristics that favor increased growth and reduced reproduction. These characteristics resulted in decreased predation of adults by gape-limited predators and a greater ability to cope with heavy parasite burdens. P. columbiana exhibited slower growth, which resulted in increased predation although higher reproduction rates may compensate.The major effect of heavy metals on species distributions was indirect on the snails' parasites. Parasites appeared to be very susceptible to metals, and this resulted in lower parasite diversity and intensities at polluted sites for both species of snails. P. columbiana may only be able to outcompete L. palustris at polluted sites due to the indirect effects of heavy metals; the negative effect of heavy metals on parasites, and a proposed negative effect of metals on the foraging ability of sunfish that favors the faster-reproducing P. columbiana.

Animals↗

PubMed2004

snail expression during embryonic development of the coral Acropora: blurring the diploblast/triploblast divide?

Although corals are nominally diploblastic, the early development of Acropora millepora involves a process that clearly resembles gastrulation in higher metazoans. This similarity at the morphological level led us to search for the Acropora equivalents of genes whose key roles in gastrulation are conserved across the higher Metazoa. We here report the characterisation of one such gene, snail, which in both Drosophila and the mouse is expressed in cells undergoing an epithelial-mesenchyme transition and/or morphogenetic movements. In addition to an N-terminal SNAG domain, the Acropora snail protein contains four zinc fingers with sequences diagnostic for members of the snail protein subfamily. In situ hybridisation reveals expression in epithelial tissue in the central portion of one side of the flattened pre-gastrulation embryo, which continues to express snail as it is engulfed by its opposite layer. Comparison to snail expression during gastrulation in bilaterians such as Drosophila reveals striking similarities and suggests mechanistic, and possibly evolutionary, links between the processes of mesoderm formation in bilaterians and endoderm formation in the Cnidaria.

Amino Acid Sequence↗

PubMed1999

Snail-type zinc finger proteins prevent neurogenesis in Scutoid and transgenic animals of Drosophila.

Scutoid is a classical dominant gain-of-function mutation of Drosophila, causing a loss of bristles and roughening of the compound eye. Previous genetic and molecular analyses have shown that Scutoid is associated with a chromosomal transposition resulting in a fusion of no-oceli and snail genes. How this gene fusion event leads to the defects in neurogenesis was not known until now. Here have found that snail is ectopically expressed in the eye-antennal and wing imaginal discs in Scutoid larvae, and that this expression is reduced in Scutoid revertants. We have also shown that the expressivity of Scutoid is enhanced by zeste mutations. snail and escargot encode evolutionarily conserved zinc-finger proteins involved in the development of mesoderm and limbs. Snail and Escargot proteins share a common target DNA sequence with the basic helix-loop-helix (bHLH) type proneural gene products. When expressed in the developing external sense organ precursors of the thorax and the eye, these proteins cause a loss of mechanosensory bristles in the thorax and perturbed the development of the compound eye. Such phenotypes resemble those associated with Scutoid. Furthermore, the effect of ectopic Escargot on bristle development is antagonized by coexpression of the bHLH gene asense. Thus, our results suggest that the Scutoid phenotype is due to an ectopic snail expression under the control of no-oceli enhancer, antagonizing neurogenesis through its inhibitory interaction with bHLH proteins.

Animals↗

PubMed1999

Characterisation of the human snail (SNAI1) gene and exclusion as a major disease gene in craniosynostosis.

The Snail family of proteins in vertebrates comprises two zinc-finger transcription factors, Snail and Slug, which are thought to be involved in the formation of the mesoderm and neural crest. Here, we describe the isolation and characterisation of the human Snail (SNAI1) gene and a related Snail-like pseudogene, SNAI1P. SNAI1 spans approximately 6.4kb, contains three exons and has a CpG island upstream of the coding sequence. A single transcript of 1.9 kb was detected in several human foetal tissues, with the highest expression in the kidney. The SNAI1 open reading frame encodes a protein of 264 amino acids containing four zinc-finger motifs that show 87.1% identity to mouse Snail (mSna). SNAI1 was mapped to chromosome band 20q13.1 and is likely to lie between markers D20S109 and D20S196. Investigation of SNAI1 coding sequences by single-strand conformation polymorphism analysis excluded SNAI1 as a major disease gene in craniosynostosis. Two single nucleotide polymorphisms encoding synonymous amino acids were identified in exon 2. The SNAI1P pseudogene was isolated, sequenced and mapped to chromosome band 2q34.

Amino Acid Sequence↗

PubMed2006

Octopamine boosts snail locomotion: behavioural and cellular analysis.

We measured the reduction in locomotion of unrestrained pond snails, Lymnaea stagnalis, subsequent to transdermal application of two selective octopamine antagonists, epinastine and phentolamine. After 3 h in fresh standard snail water following treatment with 4 mM epinastine or 3.5 mM phentolamine, the snails' speed was reduced to 25 and 56% of the controls (P < 0.001 and P = 0.02, respectively). The snails' speed decreased as the drug concentration increased. In the isolated CNS, 0.5 mM octopamine increased the firing rate of the pedal A cluster motoneurons, which innervate the cilia of the foot. In normal saline the increase was 26% and in a high magnesium/low calcium saline 22% (P < 0.05 and 0.01, respectively). We conclude that octopamine is likely to modulate snail locomotion, partially through effects on pedal motoneurons.

Adrenergic alpha-Agonists↗

PubMed2006

Protein synthesis-dependent reactivation of a contextual conditioned reflex in the common snail.

We report here a study of the effects of blockade of protein synthesis with anisomycin during reactivation of a contextual conditioned reflex in the common snail. The amplitudes of the defensive reactions of snails to standard tactile stimulation before training were identical in two conditions: 1) testing of responses of snails fixed by the shell to a plastic ball floating in water and 2) on the surface of the terrarium glass. After applying electric shocks to the snails' skin for 5 days, a significant difference in responses reflecting the formation of a contextual conditioned reflex was seen in only one of the contexts. Placing trained snails in the same context (reminding) two days after training with simultaneous injection of anisomycin led to significant weakening of training, while control injections of physiological saline produced no such changes. These data suggest that the mechanisms of memory consolidation after training and reminding are not identical.

Animals↗

PubMed2006

The effects of changes in extracellular calcium concentrations on the electrical properties of command neurons after acquisition of a defensive conditioned reflex in snails.

Studies of the electrical characteristics of the command neurons of a defensive reflex showed that the membrane potential showed no significant changes in response to changes in the calcium concentration in the perfusing solution in either intact or trained snails. Increases in the calcium ion concentration in intact snails were accompanied by increases in the threshold potential, from 14 +/- 0.7 mV at 2.5 mM Ca2+ to 21.8 +/- 0.9 mV at 20 mM Ca2+. The threshold potential in trained snails decreased in response to both increases and decreases in calcium concentrations, from 16.8 +/- 0.6 mV (physiological saline containing 10 mM Ca2+) to 13.3 +/- 0.6 mV at 20 mM Ca2+ and 11.8 +/- 0.8 mV at 2.5 mM Ca2+. The critical depolarization level changed correspondingly: in intact snails, this decreased with increases in calcium concentration, while in trained snails it increased in response to both increases and decreases in the calcium concentration.

Animals↗

PubMed1993

The introduction of Melanoides tuberculata (Mollusca: Thiaridae) to the island of Saint Lucia (West Indies) and its role in the decline of Biomphalaria glabrata, the snail intermediate host of Schistosoma mansoni.

A malacological survey was carried out in May 1992 in the whole hydrographic system of Saint Lucia 11 years after the end of a biological control programme to eliminate Biomphalaria glabrata, the snail intermediate host of Schistosoma mansoni. A competitor snail, Melanoides tuberculata, was introduced to Saint Lucia in 1978 and field experiments in several habitats were conducted by Prentice between 1978 and 1986. At the present time M. tuberculata is the most common freshwater snail in Saint Lucia. The results of the survey, undertaken in sites where B. glabrata occurred in large populations in the past showed (i) the absence of the snail hosts from seven sites now extensively colonized by the competitor (ii) the presence of B. glabrata in low or very low densities in 17 sites together with the competitor and (iii) the presence of the intermediate hosts in large populations in only two sites where M. tuberculata was absent. These results confirm the positive results observed by Prentice. The presence of another planorbid snail, B. straminea, is reported for the first time in Saint Lucia.

Animals↗

PubMed1996

The influence of aestivation in land snails on the larval development of Muellerius cf. capillaris (Metastrongyloidea: Protostrongylidae).

The larval development of Muellerius cf. capillaris in aestivating Trochoidea seetzenii and Theba pisana was delayed: in the first snail 82% of the parasites remained as second-stage larvae (L2) after as much as 90 days, and in the second snail 60% remained as L2 after 50 days. Reactivation of T. seetzenii after 59 days of aestivation caused the larvae to develop to the third stage (L3). The number of recovered larvae among T. seetzenii was consistently higher in active vs aestivating snails (P < 0.05). Such differences were not evident among T. pisana (P > 0.05). In active T. pisana, larval development was faster than in active T. seetzenii, whereas there were no such differences between aestivating snails of these 2 species. Aestivating infected T. seetzenii had lower body weights than same-size active non-infected, as well as infected snails. Aestivating infected T. pisana were not weighed, but they too exhibited poor body condition.

Analysis of Variance↗

PubMed1987

Field evaluation of controlled release copper glass as a molluscicide in snail control.

Limited field evaluation of a new molluscicide, copper controlled release glass (CRG), was carried out in 4 human water contact sites in shallow and slow flowing streams in the highveld region of Zimbabwe during 1984 to 1986. The results indicate that the copper CRG has great potential as an inexpensive snail control agent to reduce schistosomiasis transmission. There was a marked reduction in snail numbers in the treated sites after application of 2 forms of the copper molluscicide; a "fast" CRG with approximately 24-h solution time in water and a "slow" CRG with about 1-year solution time. Snail numbers remained depressed during the observation period while frogs and fish were not affected. Fluctuations in snail numbers in the untreated sites showed no clear pattern, being erratic and unpredictable and probably attributable to seasonal effects. Problems of the correct amounts of molluscicide to apply to a site are to an extent overcome by knowledge of the copper binding capacity of the mud substrate. The mud sediment can be saturated by the "fast" release copper glass to achieve a snail killing concentration in the water which can be sustained by the "slow" release glass. It appears that the main difficulty in maintaining desirable copper levels in the water is flow, which causes rapid removal of copper from the treated waterbody. Thus, under field conditions on the highveld region of Zimbabwe, the CRG molluscicide is likely to be effective only during the stable conditions of the dry season which is, however, the main transmission period.

Animals↗

PubMed1991

Isolation of a phosphoryl choline-binding protein from the hemolymph of the snail, Achatina fulica.

A phosphorylcholine-binding protein from the hemolymph of the snail Achatina fulica was purified to near homogeneity using a Sepharose phenylphosphorylcholine affinity column. The protein bound to the affinity column was eluted with 5 mM phosphorylcholine as a single symmetrical peak. The purified protein (400 Kda) contained 35-40% carbohydrate. On SDS-PAGE the protein separated into two bands of 20 and 24 Kda, and had a pI of 5.9. On immunodiffusion, antiserum to the snail phosphorylcholine binding protein did not cross-react against other phosphorylcholine binding proteins, like rat serum phosphorylcholine-binding protein (PCBP), limulus C-reactive protein (CRP), or human CRP. On pretreatment of the snail hemolymph with this antiserum, the hemagglutination titer of the hemolymph was markedly decreased. The purified snail phosphorylcholine binding protein agglutinated rabbit erythrocytes in the absence of divalent cation (Ca+2) but trace amount of Ca+2 increased its binding. The strongest inhibitor of the agglutination reaction was lactose, followed by melibiose and 2-deoxygalactose. The relationships of the snail phosphorylcholine binding protein to other hemolymph agglutinins and to CRPs are discussed in light of common phylogeny.

Animals↗

PubMed1991

"Central arousal" and sexual responsiveness in the snail, Helix aspersa.

In molluscs, a "central arousal" system is thought to positively modulate both an animal's level of activity and its behavioral responsiveness. This hypothesis is examined in Helix aspersa by testing the relationships between activity, feeding, and sexual behavior. Activity, feeding, and mating exhibit parallel daily rhythms. Snails are most active, and eat and mate most frequently, during scotophase and the first 3 h of photophase. Handling and injections of serotonin (5 x 10(-7) m/kg body wt) increase general activity. Inducing activity during late photophase increases food consumption, but it does not induce sexual activity. Moreover, serotonin and handling have no effect on sexual arousal; treated snails show no increase in genital eversion stage and require the same length of courtship as controls. If snails are sexually deprived, increasing activity in late photophase does increase copulation frequency, but snails do not copulate more frequently than do unhandled snails tested during early photophase. These results suggest that while manipulations thought to increase central arousal do increase activity and responsiveness to food stimuli, they do not directly affect sexual proclivity or sexual arousal. Moreover, the relationship between feeding and sexual behavior differs between Helix and Aplysia. This difference between the two species may be related to the differences in their reproductive strategies.

Animals↗

PubMed1995

Distribution of fasciolosis in Kansas, with results of experimental snail susceptibility studies.

A total of 278 veterinarians throughout Kansas were sent mail-in survey forms asking specific questions relating to their experience with fasciolosis in their practice area. Replies were received from 178 (64%) veterinarians representing six practice types; one-third reported having seen cases of fasciolosis in their practice. The results of our survey indicate that the majority of the cattle diagnosed with liver fluke disease in Kansas are imported from other areas of the USA. However, in both central and southeastern regions of Kansas, some cattle that had never been out of the state were infected with Fasciola hepatica. Thus, these areas of Kansas should be considered endemic for liver fluke disease. Methods of diagnosis, types of operations, and improvements seen after treatment were also discussed. In order to ascertain the existence of one or more possible snail intermediate hosts within Kansas, five species of lymnaeid snails were collected from central and southeastern parts of the state and tested for their susceptibility to infection by Fasciola hepatica. The snails collected included Pseudosuccinea columella, Fossaria obrussa, Fossaria bulimoides, Fossaria parva and Fossaria dalli. Of these, Pseudosuccinea columella and Fossaria bulimoides proved susceptible to experimental infection by Fasciola hepatica. Metacercariae obtained from experimentally infected snails were used to infect both a weanling calf thereby completing the life cycle of the parasite. This report is the first to identify the existence of suitable snail intermediate hosts for Fasciola hepatica in Kansas.

Animals↗

PubMed1987

Neural mechanisms of age-dependent changes in avoidance behaviour of the snail Helix lucorum.

In order to study the emergence of different components of learning and memory, we investigated developmental changes in behavioural, neurophysiological and histochemical experiments in newborn and adult terrestrial snails (Helix lucorum L.). The absence of sensitization and inability to develop avoidance-conditioned reactions were revealed in behavioral experiments in juvenile snails under 1 month old. Investigation of neural mechanisms of this behavioral deficit showed the absence of sensitization in spike reactions to repeated nerve stimulation in command neurons for the avoidance behaviour in juvenile snails. The same dynamics of response amplitude, as in juvenile snails, was seen in adults only after selective impairment of serotonergic neurons by treatment with 5,7-dihydroxytryptamine. During 1 month after hatching, the serotonin content investigated with fluorescence techniques was very low in the nervous system. This result suggests that the absence of sensitization, as well as inability to be aversively conditioned is related to 5-hydroxytryptamine level, which changes during postnatal development in the snail.

Action Potentials↗