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At least 1,081 records · Page 60Linked to original sources
PubMed1996

Effect of serotonin and neuropeptides on adenylate cyclase of the central nervous system and peripheral organs of the freshwater snail Planorbarius corneus.

The effect of serotonin, FMRFamide and the small cardioactive peptide B (SCPB) on adenylate cyclase activity of the central nervous system and some peripheral organs of the freshwater snail Planorbarius corneus was investigated. The amine and the cardioactive peptide stimulated the enzyme, although with different potencies, in all tissues studied and, when tested in combination, an additive activation was obtained. FMRFamide induced differential effects in the various targets: marked stimulation of adenylate cyclase, additive to that provoked by serotonin or SCPB, in salivary glands; inhibition of the enzyme, both alone and in combination with the other neuromediators, in the nervous tissue; whereas no influence was found in adenylate cyclase activity in the buccal mass. In the last of these tissues, the peptide might act through an intracellular second messenger other than cyclic AMP. The responsiveness of adenylate cyclase to these neuromediators in all the central ganglia suggested that they can exert an important role as neurotransmitters and/or neuromodulators in the central nervous system of the snail. Moreover, in the light of the differential sensitivity of adenylate cyclase in the salivary glands and buccal mass, we suggest that serotonin, FMRFamide and SCPB modulate the feeding behaviour of P. corneus in a complex way.

Adenylyl Cyclases↗
PubMed1990

Locomotion in the pulmonate snail Melampus--II. Recovery after pedal ganglion excision.

1. When one pedal ganglion is removed, snails first crawl using the unoperated side of the foot, but in 4-8 weeks the operated side exhibits an anterior-to-posterior gradient of recovery. 2. A ganglion bud bridges the site of the missing ganglion and axons project from intact central ganglia into the foot. 3. Rhythmic activity in right and left pedal nerve pairs is correlated during locomotion in the regenerated snails. 4. The oscillator in the remaining pedal ganglion drives bilaterally coordinated activity. Regenerated projections from the cerebral ganglia through the bud to the remaining pedal ganglion suffice to initiate locomotion.

Animals↗
PubMed1990

Increased mortality in land snails (Cepaea nemoralis) exposed to powerline (60-Hz) magnetic fields and effects of the light-dark cycle.

The effects of various durations (0.5, 2, 12, 48, or 120 h) of day- and night-time exposures to a 1.0 gauss (rms) 60-Hz magnetic field or sham field on mortality levels in the nocturnally-crepuscularly active land snail, Cepaea nemoralis, were examined. These snails were injected with morphine or saline vehicle and tested for reaction to an aversive thermal stimulus as part of another study. Mortality levels were monitored over a 2-week period following the initial exposure to the fields and were shown not to be differentially affected by the drug injection procedures. Mortality levels increased linearly as a function of increased length of exposure to the magnetic fields (P less than 0.001) but not when exposed to the sham fields. As well, night-time exposures resulted in greater mortality levels than day-time exposures (P less than 0.025). These results indicate that day-night rhythms are important in determining the magnitude of the magnetic field exposure effect. It is speculated that the magnetic fields may disrupt endogenous opioid- and calcium-modulated homeostatic mechanisms and augment stress effects, modifying a variety of systems including immunocompetence.

Animals↗
PubMed1996

Nitric oxide, but not serotonin, is involved in acquisition of food-attraction conditioning in the snail Helix pomatia.

The effects of inhibition of nitric oxide (NO) or serotonin (injection of nitro-L-arginine methyl ester (L-NAME) or 5,6-dihydroxytryptamine (5,6-DHT), respectively) on food-attraction conditioning was investigated in Helix. Blocking NO synthase (NOS) prior to conditioning significantly impaired the food-finding ability of the snails. Food-conditioned snails, after inhibition of NOS, remained able to locate the conditioned food. These results indicate that the acquisition of memory depends on NO, whereas memory recall and olfactory orientation are not dependent. Ablating the serotonergic system did not influence food-attraction conditioning, suggesting that food-attraction conditioning may be at variance with conventional associative conditioning procedures.

5,6-Dihydroxytryptamine↗
PubMed1996

MDL 12330A inhibits the non-neuronal adenylyl cyclase from the freshwater snail Planorbarius corneus, but the neuronal enzyme is activated by this compound.

N-(Cis-2-phenyl-cyclopentyl)azacyclotridecan-2-imine-hydrochloride (MDL 12330A), considered an inhibitor of adenylyl cyclase, has been tested on the enzyme activity of neuronal and non-neuronal tissues from the freshwater snail Planorbarius corneus. The drug dose-dependently activates the basal as well as agonist-stimulated adenylyl cyclase in the ganglionic preparations, while it exerts an inhibitory effect on the enzyme present in the non-nervous tissues examined. SQ 22536 and forskolin, respectively an inhibitor and activator of adenylyl cyclase, behave as generally reported both in central and peripheral tissues of the snail. This is, to our knowledge, the first report of a stimulatory action of MDL 12330A on an adenylyl cyclase system.

Adenylyl Cyclases↗
PubMed1987

Suitability of six lymnaeid snails for infection with Fasciola hepatica.

The suitability of Fossaria (Bakerilymnaea) cubensis and Pseudosuccinea columella from Louisiana as intermediate hosts for Fasciola hepatica was compared to P. columella and Stagnicola elodes from Ann Arbor, MI, S. attenuata from Hidalgo, Mexico, Lymnaea gedrosiana from Iran and L. natalensis from Senegal. P. columella from LA was shown to be a more suitable host (51.3% became infected) than F. (B.) cubensis (15.2% and 26.4% of two populations became infected). The infection rate for P. columella from MI, was 50% and for L. gedrosiana was 32.5%, whereas L. natalensis, S. elodes and S. attenuata were refractory. F. (B.) cubensis and P. columella have some degree of suitability as intermediate hosts for F. hepatica under laboratory conditions, but field observations of their habitat in southern LA and characteristic management of cattle indicate that the former snail is more important as an intermediate host in this enzootic area. Tissue sections of suitable snails had few histopathological effects but physical damage caused by rediae was pronounced, mainly in the digestive gland and in the mantle.

Animals↗
PubMed1985

Horseshoe crab (Limulus polyphemus) lectin but not garden snail (Helix pomatia) lectin elicits insulin-like activities in vitro.

Lectins from the horseshoe crab (Limulus polyphemus) and the garden snail (Helix pomatia) were tested for insulinomimetic activities in isolated rat epididymal adipocytes. The sialic acid binding horseshoe crab lectin suppressed epinephrine-induced lipolysis and augmented lipogenesis from D-[3-3H]-glucose while the N-acetylgalactosamine binding snail lectin was inactive. The results suggest that the insulin receptor on rat adipocytes contains sialic acid in its carbohydrate moiety but does not possess non-reducing alpha-D-galactopyranosyl or 2-acetamido-2-deoxy-alpha-D-galactopyranosyl end groups.

Adipose Tissue↗
PubMed1983

Inhibition kinetics of certain organophosphorus and carbamate pesticides on acetylcholinesterase from the snail Lymnaea acuminata.

k2, Kd and ki, for 2 organophosphorus (Phorate and Formothion) and 2 carbamate pesticides (Mexacarbate and Carbaryl) using acetylcholinesterase present in homogenates of the nervous tissue of the snail Lymnaea acuminata, were determined. Calculation of zero time velocities demonstrated that even in their P-S form the organophosphate compounds inhibited snail acetylcholinesterase. The kinetic constants of the 2 carbamates have been explained on the basis of their structure. The toxicity of the 4 pesticides has been explained on the basis of their kinetic constants.

Acetylcholinesterase↗
PubMed1984

Patterns of accumulation, distribution and liberation of Zn, Cu, Cd and Pb in different organs of the land snail Helix pomatia L.

The snail Helix pomatia was fed lettuce enriched with zinc, cadmium, lead and copper for 32 days, followed by a feeding period of 40-50 days with uncontaminated lettuce. The time-dependent distribution of the four metals during loading and unloading was determined in all major organs. Four general types of response to metal loading have been distinguished. Another general feature is the rhythmic nature of accumulation and de-accumulation of metals in several organs. On the other hand, each metal also elicits specific responses which can be described in terms of acute or delayed reaction and long-term accumulation. Lead is accumulated by most organs and redistributed after loading has stopped, but a single organ, the midgut gland, accumulates about 90% of this metal. Zinc accumulates in most organs during the first part of the loading period and is then redistributed to the midgut gland which may hold up to 70% of the metal at the end of the experiment. Cadmium is not taken up at all by a number of organs but the midgut gland and anterior gut keep accumulating it. After loading has been terminated the metal appears to move from the midgut gland to the gut. Copper is distributed more evenly than the other metals in the organs of the snail, the midgut gland not playing a dominant role in the storage of this metal.

Animals↗
PubMed1985

Purification and characterization of an antibacterial factor from snail mucus.

The antibacterial factor from the body surface of the African giant snail, Achatina fulica Férussac, was isolated by DEAE-Toyopearl 650M ion exchange chromatography. The isolated preparation exhibited highly positive antibacterial activity both for the Gram-positive bacteria, Bacillus subtilis and Staphylococcus aureus and for the Gram-negative bacteria, Escherichia coli and Pseudomonas aeruginosa, but it lost such activity when heated at 75 degrees C for 5 min. The antibacterial factor of the snail mucus was a glycoprotein whose molecular weight (MW) was about 160,000. It was composed of two subunits of MW 70,000-80,000.

Animals↗
PubMed1987

Effects of synthetic omega-conotoxin GVIA (omega-CgTX GVIA) on the membrane calcium current of an identifiable giant neurone, d-RPLN, of an African giant snail (Achatina fulica Ferussac), measured under the voltage clamp condition.

1. The sodium and the calcium inward currents (INa and ICa) of an identifiable giant neurone, d-RPLN (dorsal-right parietal large neurone), of an African giant snail (Achatina fulica Férussac), were measured separately under the voltage clamp condition. 2. The effects of synthetic omega-conotoxin GVIA (omega-CgTX GVIA) on the calcium current of the neuromembrane were examined. 3. omega-CgTX GVIA is a peptide venom originally isolated from a fish-hunting marine snail (Conus geographus L.); the peptide venom has been demonstrated to block markedly calcium channels in vertebrates. 4. In the case of the d-RPLN membrane, the ICa was much larger than INa. The command voltage (Vc) to get the ICa in maximum was about 0 mV; the maximum value of ICa in a representative experimental case, was measured as approximately 0.8 microA. 5. With respect to the ICa of a molluscan giant neurone, d-RPLN, synthetic omega-CgTX GVIA at a high concentration, 5 X 10(-5) M, showed almost no effect, in spite of reporting the peptide venom affecting the ICa in vertebrate preparations.

Amino Acid Sequence↗
PubMed1991

The effect of oxytocin on potential-dependent calcium current in snail neurons, Helix pomatia.

1. The effect of external application of oxytocin on inward calcium current in dialyzed snail neurons has been investigated under clamp conditions. 2. External application of oxytocin in a dose-dependent manner (Kd 0.9 microM) inhibits inward calcium current in dialyzed neurons of the snail, Helix pomatia. 3. Inhibition of calcium current developed with the time constant of about 2 min. The degree of restoration of calcium current after oxytocin washout depends on duration of oxytocin action. 4. It has been suggested that inhibition of calcium current by oxytocin occurs in two stages, the initial one is more fast and reversible and the second one--more slow and irreversible. The participation of soluble second messengers in the inhibitory effect of oxytocin on calcium current is discussed.

Animals↗
PubMed1995

Bursting firing of action potentials in central snail neurons elicited by d-amphetamine: role of the electrogenic sodium pump.

The effects of d-amphetamine on central neurons were studied electrophysiologically in the identifiable RP4 neuron of the African snail, Achatina fulica Ferussac. d-Amphetamine elicited bursting activity from the central RP4 neuron in a concentration-dependent manner. The bursting activity was not blocked in a high magnesium (30 mM) medium, or after a continuous perfusion of propranolol, prazosin, haloperidol, phenobarbital, hexamethonium, d-tubocurarine, atropine, or calcium-free solution containing EDTA or verapamil. These results suggested that the bursting activity elicited by d-amphetamine was not due to: (1) the synaptic effects of neurotransmitters; or (2) the cholinergic or adrenergic receptors of the excitable membrane. However, the bursting activity elicited by d-amphetamine was blocked in the presence of ouabain or in the medium containing potassium-free, low sodium solutions. d-Amphetamine did not elicit the bursting activity of the LP4 neuron in the same ganglia preparation, and did not alter the GABA-elicited currents of the snail neuron. It is concluded, therefore, that d-amphetamine induced a potassium- and sodium-dependent bursting activity of central neurons. The bursting activity of the central neuron may be associated with the sodium pump of the neuron.

Action Potentials↗
PubMed1988

Morphological and functional reconsideration of the cytoplasmic bridges which connect male germ cells in snails.

Cytoplasmic bridges (CB) between male germ cells of three fresh-water snails have been examined by electron microscopy, using ultrathin sections and freeze-fracture replicas prepared by ordinary methods and after use of filipin for indicating the presence of membrane cholesterol. The bridge plasma membrane, which was formerly considered to be smooth, was found in these snails to be corrugated. The corrugations were periodically parallel and oriented parallel to the axis of the bridge. The mature bridges showed very low densities of intramembranous particles. No filipin-sterol complexes formed on either the P face or the E face of the bridge plasma membrane, in contrast to plasma membranes elsewhere. The numbers of corrugations in each CB varied with the species. The membrane corrugations overlie bundles of electron dense fibers measuring approximately 30 nm in diameter and 60 nm in center-to-center distance, fitting into convexities of the plasma membrane. The present observations lead us to the necessity of reconsidering the morphological and functional aspects of cytoplasmic bridges in vertebrate as well as in invertebrate germ cells.

Animals↗
PubMed2005

Distribution and ontogeny of glial fibrillary acidic protein in the snail Megalobulimus abbreviatus.

Glial fibrillary acidic protein (GFAP) is the major component of intermediate glial filaments in the central nervous system of many vertebrates and invertebrates. In vertebrates, this protein is mainly expressed in mature astrocytes and provides structural cell stability. The highly conserved structure and glial specificity of this protein have allowed studies of ontogeny and phylogeny using antibodies. The present study investigated the ontogenetic profile and molecular weight of GFAP in the snail, Megalobulimus abbreviatus, particularly in cerebral ganglia and subesophageal mass, by immunohistochemistry and immunoblotting. Our results confirm and extend previous studies about glial intermediate filaments in snails, showing: (i) a higher GFAP content in cerebral ganglia than in subesophageal mass; (ii) a developmental increase of GFAP immunocontent in cerebral ganglia, as described in Vertebrates; and (iii) an electrophoretic band for GFAP of approximately 55 kDa.

Animals↗
PubMed2005

Of Snail, mice, and women.

Mechanisms for breast cancer recurrence and metastases are poorly understood. New evidence from a transgenic mouse mammary tumor model suggests that the transcriptional repressor, Snail, may play a role in recurrence by downregulating E-cadherin and inducing an epithelial-to-mesenchymal transition. Preliminary information from expression microarray data sets from primary human breast cancers suggests that high levels of Snail are correlated with poor clinical outcome for women with early breast cancer. The identification of a molecular pathway involved in mammary tumor recurrence in a mouse model offers both opportunity and challenge to confirm, extend, and exploit these findings in the clinic.

Animals↗
PubMed2005

Unraveling signalling cascades for the Snail family of transcription factors.

During development and carcinogenesis, the gradient of different molecular factors, the availability of corresponding receptors and the interplay between different signalling cascades combine to orchestrate the different stages. A good understanding of both developmental processes and oncogenesis leads to new insights into normal and aberrant regulation, processes that share some mutual key players. In this review, we will focus on the Snail family of transcription factors. These proteins, which share an evolutionarily conserved role in invertebrates and vertebrates, are implicated in several developmental processes, but are involved in carcinogenesis as well. We will highlight the different signalling cascades leading to the expression of Snail and Slug and how these factors are regulated on the transcriptional level. Then we will focus on how these factors execute their functions by repression of the numerous target genes that have been described to date.

Animals↗
PubMed2004

Integrated assessment of heavy metal (Pb, Zn, Cd) highway pollution: bioaccumulation in soil, Graminaceae and land snails.

To assess the contamination induced by traffic at the vicinity of a highway (A31, France), several complementary studies were carried out on two sites, with different profiles and traffic intensity. Concentrations of zinc, lead and cadmium were measured by atomic absorption spectrophotometry in deposits, roadside soil and autochthonous plants (Graminaceae) gathered at the vicinity of the highway (1-320 m), and in the viscera of snails Helix aspersa, transferred as sentinel in the sites. According to the results obtained for different compartments, the highway induces a contamination on the surrounding environment, up to 320 m, but with the maximum contamination observed between 5 and 20 m: the concentrations measured in plants at the vicinity of the highway were 2.1 mg Pb kg(-1) DW, 0.06 mg Cd kg(-1) DW, 62 mg Zn kg(-1) DW and the concentrations measured in snails were 21.3 mg Pb kg(-1) DW, 5.7 mg Cd kg(-1) DW, 510.8 mg Zn kg(-1) DW. The levels measured decreased with increasing distance from the highway. Results of the three metals studied indicated that lead seems to be the best metal to evaluate road transport contamination.

Analysis of Variance↗