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PubMed2002

The effect of antibiotic treatment on the supercooling ability of the land snail Helix aspersa (Gastropoda: Pulmonata).

The land snail Helix aspersa is a partially freezing tolerant species whose supercooling ability is limited to ca. -3 to -5 degrees C. One hundred adult snails were subjected to the following two experimental conditions: (i) a starved group, provided with water; (ii) an antibiotic-treated group that was provided with a solution containing a mixture of two antibiotics. The antibiotic group exhibited a T(c) significantly lower than the starved group (-3.94 +/- 1.32 degrees C, n = 40 and -3.07 +/- 0.99, n = 30, t test, p < 0.005). This study showed that bacteria of the gut are likely to elevate animal supercooling points. It is also the first report in which a possible ice-nucleating activity of the gut microflora in a land snail has been suggested by the action of antibiotics on the T(c).

Acclimatization↗

PubMed1997

Effects of cardioactive peptides on myocardial cAMP levels in the snail Helix aspersa.

Several cardioactive peptides from the pulmonate snail Helix aspersa were tested for their effects on myocardial cAMP levels, but only the family of small cardioactive peptides (SCPs) were clearly effective. SCP increased cAMP in a dose dependent manner; the time course was phasic. The structure-activity relations of this effect were examined with a set of 3 synthetic analogs having characteristics, at the carboxyterminal, of both the SCPs and FMRFamide-related peptides. The adenylate cyclase activator forskolin mimicked the mechanical effect of SCPs on the heartbeat. We conclude that the effect of SCPs on the Helix heart may be mediated by cAMP.

Animals↗

PubMed1997

Biochemical characterization and histochemical localization of nitric oxide synthase in the nervous system of the snail, Helix pomatia.

Nitric oxide synthase (NOS) in the snail Helix pomatia was characterized by biochemical and molecular biological techniques and localized by histochemical methods. Central ganglia contained particulate paraformaldehyde-sensitive and cytosolic paraformaldehyde-insensitive NADPH-diaphorase. The cytosolic NADPH-diaphorase activity coeluted with NOS activity. The activity of NOS was dependent on Ca2+ and NADPH and was inhibited by N(G)-nitro-L-arginine (L-NNA). Proteins purified by 2',5'-ADP affinity chromatography were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and migrated at 150, 60, 40, and 30 kDa. An antibody to mammalian NOS exclusively labeled the 60-kDa protein. Characterization of the cDNA of the corresponding 60-kDa NOS-immunoreactive protein revealed no sequence homology with any known NOS isoform. The recombinant protein exhibited Ca2+- and NADPH-dependent NOS activity, which was partially inhibited by EGTA and L-NNA. Histochemistry showed NADPH-diaphorase activity in discrete regions of the central and peripheral nervous system. About 60% of the NADPH-diaphorase-positive neurons colocalize with immunoreactive material detected by antibodies to mammalian NOS. Comparison of organs showed the highest NADPH-diaphorase activity in the nervous system, whereas moderate activity was present in muscle tissue, digestive tract, and gonads. Our study suggests the presence of NOS and a putative NOS-associated/regulating protein in mollusk nervous tissue.

Animals↗

PubMed2004

Nitric oxide synthesis is blocked in the enteral nervous system during dormant periods of the snail Helix lucorum.

During dormancy of terrestrial snails, the whole neuromodulation of the nervous system is deeply modified. In this work we studied the adaptation of a previously described, putatively nitric oxide (NO) forming enteral network to the long-term resting periods of the snail Helix lucorum. The standard NADPH diaphorase (NADPHd) technique, which is an accepted method for histochemical NO synthase (NOS) detection, labeled the same enteric neurons of the midintestine in active or hibernated snails. Quantification of the NO-derived nitrite by the Griess reaction established that the nitrite formation is confined to the NADPHd-reactive network containing the midintestinal segment. In active snails, the nitrite formation could be enhanced by the NOS substrate L-arginine (10 microM-1 mM), but decreased by the known NOS inhibitors 1 mM N(omega)-nitro-L-arginine (NOARG) and 10 mM aminoguanidine (AG). Application of 1 mM L-arginine and 1 mM NOARG decreased the amplitude of the midintestinal muscle contractile activity, but did not affect the rectal motility. In dormancy, the nitrite formation was reduced in the NADPHd-reactive midintestinal network. Application of l-arginine could not provoke nitrite production and did not influence the midintestinal motility. Our findings indicate that NO is involved in the neural transmission to intestinal muscles of gastropods, but enteric release of NO is blocked during dormancy. The decreased NO synthesis is possibly due to an as yet undefined mechanism, by which the L-arginine/NO conversion ability of NOS could temporarily be inhibited in the long-term resting period of H. lucorum.

Animals↗

PubMed2002

Elements of cold hardiness in a littoral population of the land snail Helix aspersa (Gastropoda: Pulmonata).

The land snail Helix aspersa can be considered partially tolerant to freezing, in the sense it can survive some ice formation within its body for a limited time, and possesses a limited ability to supercool. This study aimed at understanding what factors are responsible for the variation of the temperature of crystallization ( Tc) in a littoral temperate population. The ability to supercool was maximal (ca. -5 degrees C) during dormancy periods (hibernation and aestivation) and minimal (ca. -3 degrees C) during spring and autumn, in relation with the decrease of water mass and the increase of osmolality. Tc decreased in October to remain stable through late autumn and winter; it increased quickly with the awakening of animals in April. Snails with an epiphragm had a significantly higher ability to supercool (ca. -4.8 degrees C) than snails which did not form an epiphragm (ca. -4.2 degrees C). The animals' size had a weak but significant influence on the realization of the Tc. It appeared that there was not a real cold-hardiness strategy in this population; rather a sum of parameters, varying in consequences of the external conditions and of the activity cycle, which are responsible for the enhancement of the supercooling ability during winter.

Acclimatization↗

PubMed1986

Opiates stimulate food consumption in the land snail Helix aspersa.

Morphine stimulates food consumption in the land snail Helix aspersa. This stimulation of food consumption can be blocked by naloxone, the potent opiate antagonist. In addition, this opiate-induced food consumption exhibits tolerance by the sixth day of treatment. This study further highlights opioid mechanisms in relatively simple organisms and also suggests that these mechanisms are "ancient" signal systems.

Animals↗

PubMed2002

Characterization of yellow-pigmented and motile enterococci isolated from intestines of the garden snail Helix aspersa.

AIMS: Enterococci associated with garden snails (Helix aspersa) were studied in order to obtain reliable species identification and characterization. METHODS AND RESULTS: Twelve yellow-pigmented and motile enterococci, isolated from the intestines of garden snails, were phenotypically close to Enterococcus casseliflavus, but they showed certain unusual biochemical characteristics. tRNA intergenic length polymorphism analysis (tDNA-PCR) divided all strains studied into two groups, in full agreement with biochemical test results. 16S rDNA sequencing, DNA base composition analysis and DNA-DNA hybridization results showed unambiguously that the enterococci studied belonged to the species Ent. casseliflavus. The representative strains of described ecovars were deposited in the Czech Collection of Microorganisms (CCM) as Ent. casseliflavus CCM 4868, 4869, 4870 and 4871. CONCLUSIONS: Enterococcus casseliflavus associated with garden snails can be subdivided into groups. SIGNIFICANCE AND IMPACT OF THE STUDY: Enterococcus casseliflavus differs from other enterococcal species in that it is typically associated with plants, soil, water and invertebrate animals. The different groups that can be found in these widely occurring bacteria are possibly source-specific ecovars, as exemplified by the Ent. casseliflavus inhabiting the intestines of snails.

Animals↗

PubMed1995

Properties of slow early potassium current in neurons of snail Helix pomatia.

1. In isolated neurons of visceral ganglia of snail Helix pomatia a slow early outward current (IA) was studied using a two-microelectrode voltage clamp technique. 2. The time of activation and inactivation of IAS at -40 mV were 90-120 msec and 3-5 sec respectively. The removal of inactivation at -120 mV took 2-5 min. 3. The reversal potential of the IAS was about -80 mV in normal saline and was sensitive to the external potassium concentration, changing about 35 mV per fivefold change in potassium over the range from 4 to 20 mM. The results suggest that IA were due to K+. 4. The IA persisted in Ca2+ -free medium and in the presence of Ca2+ -channels blockers, e.g., Cd2+. 5. The IA were blocked by 1-10 microM extracellular 4-aminopyridine, 1 mM of tetraethylammonium ions, 1 mM of Ba2+, but one was resistant to 1 mM Cs+. 6. 4-aminopyridine had a dual effect on the IA. It blocked the normal current, and then appeared to increase the inactivated currents.

4-Aminopyridine↗

PubMed1992

Immunochemical characterisation of tachykinin immunoreactivity in the nervous system of the garden snail, Helix aspersa.

1. Circumoesophageal ganglia and foot muscle of the garden snail, Helix aspersa, were subjected to immunocytochemistry using antisera to the tachykinins, substance P (SP), neurokinin A (NKA), kassinin (KAS) and eledoisin (ELE). 2. Immunoreactivity in neuronal somata and fibres was detected only with the SP antiserum. 3. SP and NKA radioimmunoassays were performed on extracts of circumoesophageal ganglia. In common with immunocytochemistry, immunoreactivity was only detected with the SP antiserum. 4. Gel permeation chromatography of extracts resolved a single peak of immunoreactivity eluting slightly later than synthetic mammalian SP. Reverse-phase HPLC of immunoreactive fractions resolved two immunoreactive peptides representing oxidised and reduced forms of a single peptide. 5. These data suggest that the nervous system of H. aspersa contains a single tachykinin with C-terminal structural characteristics similar to mammalian SP.

Amino Acid Sequence↗

PubMed1981

The composition of intracellular granules from the metal-accumulating cells of the common garden snail (Helix aspersa).

Certain cells in the hepatopancreas of the common garden snail (Helix aspersa) contain intracellular granules that are sites of metal-ion accumulation. These granules have been extracted and investigated by u.v. and i.r. spectroscopy, atomic-absorption spectroscopy, X-ray microanalysis, thermogravimetric analysis, enzymic assay and microanalysis. The deposits contain about 18% (w/w) water, 5% (w/w) organic matter and 76% (w/w) inorganic material of which the main components are Ca2+, Mg2+ and P2O7(4)-. The possible origin of these granules is discussed, as is their role in detoxifying heavy-metal ions.

Animals↗

PubMed2000

Topographic organization of efferent neurons with different neurochemical characters in the cerebral ganglia of the snail Helix pomatia.

This study provides a description of the organization of neurons efferent to different head areas in the cerebral ganglia of Helix pomatia, revealed by simultaneous Ni-lysine and Co-lysine back-filling of different pairs of cerebral nerves. The backfills show that labeled cerebral neurons that innervate the head areas are concentrated in seven representation foci distributed in different parts of the cerebral ganglia. Almost each head area is represented in each focus. At a gross level, the representation of the different head areas in the representation foci shows a topographic arrangement. Each focus is constituted by neurochemically different groups of neurons. All head areas are innervated by serotonin-containing fibers from a single focus (Focus 2) and by dopamine-containing fibers from Foci 1, 2, and 4. However, they are innervated by CARP and FMRFamide-containing fibers from all of the foci. The combination of retrograde labeling with 5, 6-dihydroxytriptamine induced pigment labeling of serotonin-containing neurons or with fluorescence tyrosinehydroxylase immunocytochemistry to detect dopamine-containing neurons showed that the different head areas are topographycally represented in the clusters of both the serotonin- and dopamine-containing cells. The combination of Ni-lysine backfillings from different cerebral nerves with fluorescence CARP and FMRFamide immunocytochemistry revealed that the head areas are represented also in both the CARP and FMRFamide immunoreactive groups of neurons in the different foci.

Animals↗

PubMed2005

Immunological localization of Tritonia peptide in the central and peripheral nervous system of the terrestrial snail Helix aspersa.

We report here evidence that the pedal peptides (Peps) first discovered in mollusks may be neurotransmitters with a general role in control of molluscan somatic and visceral muscles. Using Tritonia peptide (TPep) antiserum we obtained morphological evidence for such a role in Helix aspersa. We localized 1,200-1,400 small and medium-sized (5-40 microm) TPep-IR neurons in the central nervous system of Helix and demonstrated the presence of these neurons in each ganglion. Many TPep-immunoreactive (IR) neurons were motoneurons that sent axons to almost all peripheral nerves. TPep-IR fibers innervated the foot, esophagus, hermaphroditic duct, optic tentacles, salivary gland, heart, and proximal and distal aorta. In peripheral tissues TPep-IR fiber ramifications were mostly associated with muscles and with ciliated epithelia. In addition, TPep-IR fibers were in the neuropil of the ganglia, the commissures, and the connectives, and they formed axosomatic terminals in the central nervous system. TPep-IR neurons were found in the esophagus and hermaphroditic duct and as sensory receptors in the bulb of the optic tentacles. These results from Helix, and those reported elsewhere from other mollusks, suggest a general involvement of TPep-like substances in control of muscle- and ciliary-driven motor activities, including perhaps their antecedent sensory and central axosomatic integrative activity.

Animals↗

PubMed1994

Peptidergic neurons in the snail Helix pomatia: distribution of neurons in the central and peripheral nervous systems that react with an antibody raised to the insect neuropeptide, leucokinin I.

In this study, an antiserum raised against an insect myotropic peptide, leucokinin I (DPAFNSWGamide), was used for mapping leucokinin-like immunoreactive (LK-LI) neurons in the gastropod mollusc, Helix pomatia. Immunocytochemistry performed on both whole-mounts and cryostat sections demonstrated LK-LI neurons in all ganglia of the central nervous system (CNS), except the visceral ganglion. Altogether about 700 immunolabelled neurons have been found, with nearly one-half (46%) in the cerebral ganglia. A large proportion of the LK-LI neurons have small cell bodies and are likely to be interneurons. The most prominent LK-LI cell group is represented by the entire neuron population of the mesocerebri, which is the major source of a thick fiber bundle system, encircling and innervating the whole CNS. One single LK-LI giant neuron was found, which is located in the left pedal ganglion and is termed GLPdLKC (giant left pedal leucokinin immunoreactive cell). This cell has not been identified previously. The ganglion neuropils are heavily innervated by varicose LK-LI fiber arborizations. Some integrative centers, such as the medullary neuropil of the procerebri, reveal an extreme density of LK-LI innervation. All major peripheral nerves contain a large number of LK-LI axons, and LK-LI innervation is found in the musculature of different peripheral organs (buccal mass, lip, tentacles, oviduct, intestine). Among the peripheral organs investigated, the intestine contains a rich varicose LK-LI network, composed of both intrinsic and extrinsic elements. Radioimmunoassay (RIA) demonstrates a very high content of LK-LI material in Helix ganglion extracts (about 50 pmol/CNS). This is the first report on the occurrence of a substance resembling the myotropic neuropeptide leucokinin I in a phylum outside arthropods. Based on our immunocytochemical observations, a role for leucokinin-like peptides in both central and peripheral regulatory processes in Helix is suggested. According to double-labelling experiments, only a small number of the LK-LI neurons are labelled with an antibody to the vertebrate tachykinin substance P.

Amino Acid Sequence↗

PubMed1979

Motor innervation of the pharynx levator muscle of the snail, Helix pomatia: physiological and histological properties.

(1) Motor innervation of the pharynx levator muscle of Helix pomatia was investigated with intracellular recording and axonal iontophoresis of cobalt chloride. (2) Muscle fibers respond to direct electrical stimulation of the muscle with active graded responses or non-overshooting spike potentials. (3) Each fiber is innervated via the external and internal lip nerves by several (mostly 3) excitatory nerve fibers each. Two types of EPSPs can be distinguished according to amplitude, duration, and facilitation. (4) Axonal CoCl2-staining via an external lip nerve branch revealed many nerve fibers entering the muscle and branching there into a rich network of blebbed fibers of various diameters.

Animals↗

PubMed2002

Transfer of cadmium from plant leaves and vegetable flour to the snail Helix aspersa: bioaccumulation and effects.

Juvenile Helix aspersa snails were exposed for 4 weeks to fresh rape leaves (Brassica napus), contaminated by simulating superficial deposits of increasing concentrations of cadmium (Cd). The Cd concentration in leaves was 0.1 in control and 38.4, 93.1, and 177.2 microg x g(-1) (dry mass) in Cd-treated food. The concentration in snail tissues increased with increasing Cd concentrations in the food. The bioaccumulation factors ranged from 4.8 (control) to 2.4 (highest exposed group), indicating a biomagnification of Cd in this food chain. The growth of the snails treated with Cd was reduced by 17, 24, and 43% respectively, compared to the control group. Comparison of these results with those obtained with snails exposed to similar Cd concentrations in a vegetable flour revealed that accumulation and effects were relatively consistent, demonstrating a comparable bioavailability of Cd in the two diets. Tests using growing H. aspersa snails exposed to metals in flour or fresh leaves can be useful for risk assessment purposes.

Animal Feed↗

PubMed1979

Electron microscopic studies on radular tooth formation in the snails Helix pomatia L. and Limax flavus L. (Pulmonata, Stylommatophora).

The radular teeth are secreted at the posterior end of the radular gland and move slowly towards the buccal cavity where they start to function. Helix pomatia and Limax flavus were examined to determine whether the newly formed teeth already show their definite species specific shape, or whether they are gradually finished and moulded in the radular gland. Scanning electron micrographs of Helix pomatia show that teeth are secreted in the odontoblast region in their final form. Their surface is still uneven at the outset; the same is true for the newest teeth of Limax flavus. Older teeth ready for use have a smooth surface. This change seems to be brought about by secretory activity of the superior epithelium of the radular sac. Air-dried radulae, previously isolated by KOH maceration, show considerable artefacts at their posterior end. Maceration leads to shrinking of the newest teeth, but does not change their contours. The newly secreted but as yet unhardened teeth become greatly deformed during the drying process.

Cytoplasm↗

PubMed1994

Distribution and anatomy of GABA-like immunoreactive neurons in the central and peripheral nervous system of the snail Helix pomatia.

Gamma-aminobutyric acid (GABA)-like immunoreactive neurons were studied in the central and peripheral nervous system of Helix pomatia by applying immunocytochemistry on whole-mount preparations and serial paraffin sections. GABA-immunoreactive cell bodies were found in the buccal, cerebral and pedal ganglia, but only GABA-immunoreactive fibers were found in the viscero-parietal-pleural ganglion complex. The majority of GABA-immunoreactive cell bodies were located in the pedal ganglia but a few could be found in the buccal ganglia. Varicose GABA-ir fibers could be seen in the neuropil areas and in distinct areas of the cell body layer of the ganglia. The majority of GABA-ir axonal processes run into the connectives and commissures of the ganglia, indicating an important central integrative role of GABA-immunoreactive neurons. GABA may also have a peripheral role, since GABA-immunoreactive fibers could be demonstrated in peripheral nerves and the lips. Glutamate injection did not change the number or distribution of GABA-immunoreactive neurons, but induced GABA immunoreactivity in elements of the connective tissue ensheathing the muscle cells and fibers of the buccal musculature. This shows that GABA may be present in different non-neural tissues as a product of general metabolic pathways.

Animals↗

PubMed1995

In vitro capsaicin-induced cytological changes and alteration in calcium distribution in giant serotonergic neurons of the snail Helix pomatia: a light- and electron-microscopic study.

Morphological changes induced by capsaicin were studied in the serotonergic metacerebral giant neurons of the cerebral ganglia of Helix pomatia under in vitro conditions. Capsaicin at a concentration of 10(-4)M caused characteristic structural alterations in the giant serotonergic neurons but did not significantly influence serotonin immunoreactivity in the neurons. At the light-microscopic level, the most conspiciuous structural alterations were swelling of the cell bodies, which contained a swollen pale nucleus. Under the electron microscope, the nuclei, mitochondria and the cisternae of the endoplasmic reticulum were swollen in the capsaicin-affected metacerebral giant neurons. Electron-microscopic cytochemical techniques for calcium demonstration revealed electron-dense deposits in the swollen mitochondria and in the cisternae of the endoplasmic reticulum, suggesting an increased Ca2+ influx. The serotonergic metacerebral giant neurons could be labelled by cobalt (1mM) in the presence of capsaicin (10(-4)M) suggesting that capsaicin opens the cation chanels of the capsaicin-sensitive neuronal membrane. The morphological and cytochemical alterations induced by capsaicin in the serotonergic metacerebral giant neurons of Helix pomatia closely resemble those induced in sensory neurons of mammalian dorsal root ganglion.

Animals↗