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PubMed1996

Identification of two novel genes specifically expressed in the D-group neurons of the terrestrial snail CNS.

A search for genes specifically expressed in the giant interneurons of parietal ganglia of the snail Helix lucorum yielded, among others, two genes named HDS1 and HDS2. According to data obtained by Northern hybridization and whole-mount in situ hybridization, both genes are neurospecific and expressed almost exclusively in the peptidergic D-group neurons (Sakharov, 1974) located in the right parietal ganglion. In situ hybridization of the HDS1 and HDS2 probes with CNS of several related species of the Helicoidea superfamily identified in all cases similarly located homologous groups of neurons. Sequencing of the near full-length cDNA copies of the HDS1 and HDS2 genes revealed open reading frames 107 and 102 amino acids long for HDS1 and HDS2, respectively. Both putative proteins contain a hydrophobic leader peptide and putative recognition sites for furin-like and PC-like endopeptidases. Predicted amino acid sequences of the HDS1 and HDS2 proteins were found to be moderately homologous to each other, as well as to the LYCP preprohormone expressed by the light yellow cells of the freshwater snail Lymnaea stagnalis. These results confirm an earlier hypothesis that the D-group of the Helix family and the light yellow cells of Lymnaea stagnalis represent homologous neuronal groups. Our data suggest that the HDS1 and HDS2 genes encode precursors of secreted molecules, most likely neuropeptides or neurohormones.

Amino Acid Sequence↗

PubMed1996

Effectors of metabolic depression in an estivating pulmonate snail (Helix aspersa): whole animal and in vitro tissue studies.

We have examined metabolic depression in the land snail (Helix aspersa) during estivation, and have developed a tissue model of metabolic depression using an in vitro mantle preparation. The metabolic rate of H. aspersa is depressed by 84% in vivo within 4 weeks of onset of estivation, and this metabolic depression is accompanied by a decrease in haemolymph PO2 and pH, and an increase in haemolymph PCO2. The in vitro mantle preparation has a stable O2 consumption and energy charge, and an energy charge similar to that of mantle in vivo. The in vitro mantle is an O2-conforming tissue, with VO2 varying curvilinearly with PO2. Consequently, we have developed a mathematical method of calculating tissue VO2 at any PO2. These calculations show that under appropriate incubation conditions of pH and PO2, the mantle from estivating animals shows a stable in vitro metabolic depression of 48% compared to mantle from control snails. The extrinsic effects of PO2 and pH account for 70% of the total in vitro metabolic depression of mantle tissue; intrinsic effectors contribute a further 30%.

Adenosine Diphosphate↗

PubMedDate not supplied

Mechanisms of the development of sensitizations in the snail: the participation of calcium and calmodulin.

A single sensitizing exposure led to brief (up to 1 h) and prolonged (several hours) changes in the defense reactions of snails, in the activity of command neurons, as well as in the content of bound calcium in these neurons. The application of the specific calmodulin blocker, W7, or the removal of Ca2+ from the medium bathing the snail's CNS before the sensitizing exposure, exerted a suppressant influence on the development of both the brief and the prolonged behavioral and neuronal effects of sensitization. At the same time, the application of W7 or the removal of Ca2+ following the application of the sensitizing influence did not suppress the development of the prolonged changes in the command neurons. The data obtained make it possible to assume that calmodulin directly participates in the regulation of the membrane and synaptic events leading to the development of the brief effects of sensitization. In addition, it is probably involved in the initiation of the metabolic reactions leading to the occurrence of the prolonged effects; however, it does not take part directly in their manifestation.

Aggression↗

PubMedDate not supplied

Influence of leukotrienes B4 and C4, 12-hydroxyeicosatetraenoic acid, and erythro epimers of hepoxilin B3 on the plasticity of cholinoreceptors of neurons of the common snail.

The influences of a number of acyclic eicosanoids which are formed from arachidonic acid under the influence of 5- and 12-lipoxygenases on the plasticity of cholinoreceptors of neurons of the common snail, which was assessed on the basis of the degree of frequency depression of the amplitude of the inward current induced by local application of acetylcholine to the soma, were investigated in identified RPa3 and LPa3 neurons of the common snail using the method of bielectrode recording of the potential on the membrane. The plasticity of the cholinoreceptors was enhanced by leukotrienes B4 and C4, and was not altered by 12(S)-hydroxy-(5Z, 8Z, 10E, 14Z)-eicosatetraenoic acid, or by the threo and erythro epimers of hepoxilin B3. An inference is drawn regarding the regulation of the plasticity of cholinoreceptors by leukotrienes B4 and C4, which are formed under the influence of 5-lipoxygenase. One of these pathways includes inositol-1,4,5-triphosphate-dependent mobilization of deposited Ca2+.

Acetylcholine↗

PubMedDate not supplied

Molecular-cellular mechanisms of the formation of long-term memory in the edible snail.

This short review, based mainly on our own studies, summarizes data on the molecular-cellular mechanisms of non-associative and associative forms of learning (sensitization and classical conditioning) in the edible snail. A hypothesis is proposed which suggests that learning in defensive behavior command neurons in the edible snail is activated by a complex metabolic response specific for the type of conditioned habit. Excitation arriving at the neuron, in addition to activating second messenger systems, initiates the synthesis of short-lived (1-3 h) protein molecules which are specific (in the case of conditioning) or relatively specific (in the case of sensitization) for particular synaptic inputs. When training is inadequate, its effect can disappear from the point at which these proteins are degraded. When learning is better fixed, its effects last for several days (for sensitization) or significantly longer periods of time (for conditioning). Prolonged retention of habits should correspond to the situation of self-maintaining synthesis of long-lived protein molecules, which control the synthesis of synapse-specific short-lived regulator molecules.

Animals↗

PubMedDate not supplied

Serotonin imitates several of the neuronal effects of nociceptive sensitization in the common snail.

Experiments on defensive behavior command neurons in common snails showed that synaptic facilitation in the responses of nerve cells to sensory stimulation occurs 50-60 min after the onset of application of serotonin (10 microM) to the CNS. The properties of neuron electrogenic membranes (membrane potential, membrane excitability) did not change after exposure to serotonin. Along with synaptic facilitation, serotonin (100 microM) increased the excitability and produced minimal depolarization of the membranes of command neurons. Serotonin had selective effects on the reactions of neurons to different sensory stimuli: facilitation of neuron responses to tactile stimulation of the head lasted 1 h, while responses to application of dilute quinine solution lasted 2-3 h; serotonin facilitated neuron responses to tactile stimulation only of the snail's head, and did not alter the responses to stimulation of the foot or the mantle ridge. The time course of the electrophysiological effects of serotonin coincided with changes in bound calcium (Cab) levels in command neurons. This set of serotonin-induced neurophysiological effects is similar to the effects resulting from the development of nociceptive sensitization. It is suggested that serotonin is involved in the mechanisms of transient changes and consolidation of long-term plastic rearrangements in command neurons which underlie sensitization.

Animals↗

PubMed1976

Selection of auxotrophic mutants in Saccharomyces cerebisiae by a snail enzyme digestion method.

Yeast cells in the stationary phase of growth are relatively resistant to snail enzyme digestion. This resistance was shown to decrease abruptly in the course of only 3-5 duplications, when stationary cells were allowed to grow in a fresh medium. The selective digestion of growing prototrophs from a mutagenized culture in minimal medium by snail enzyme was applied to increase the proportion of auxotrophs which remained relatively resistant.

Cell Division↗

PubMed1998

Isolation and identification of chondroitin sulfates from the mud snail.

Chondroitin sulfates were isolated from the mud snail. For the quantitative analysis of enzymatic digestion products of isolated chondroitin sulfates, strong anion exchange-high performance liquid chromatography (SAX-HPLC) was performed. By the action of chondroitinase ABC, three unsaturated disaccharides 2-acetamide-2-deoxy-3-O-(beta-D-gluco-4-enepyranosyluronic acid)-D-galactose (delta Di-OS), 2-acetamide-2-deoxy-3-O-(beta-D-gluco-4-enepyranosyluronic acid)-6-O-sulfo-D-galactose (delta Di-6S) and 2-acetamide-2-deoxy-3-O-(beta-D-gluco-4-enepyranosyluronic acid)-4-O-sulfo-D-galactose (delta Di-4S) were produced from the mud snail chondroitin sulfates. The analysis showed that relative proportion of delta Di-OS/delta Di-6S/delta Di-4S was 58.7/3.1/38.2. The immunomodulating activity of chondroitin sulfate was examined by cell proliferation assay and these results suggest that it might be a immunosuppressant.

Adjuvants, Immunologic↗

PubMed2000

Hemocytic lysosome response in the snail Helix aspersa after exposure to the fungicide copper oxychloride.

This study investigated the use of lysosomal responses of hemocytes of the common garden snail, Helix aspersa, as biomarker of stress due to exposure to the fungicide copper oxychloride. The neutral red retention (NRR) time assay was employed for this purpose. Two groups of snails were exposed to 80 microg g(-1) and 240 microg g(-1) copper oxychloride in their food, respectively, for a period of 6 weeks. They were compared with a control group to which no copper oxychloride was added. The two groups exposed to the fungicide exhibited significantly higher (p < 0.001) whole body copper concentrations (200.85 +/- 53.5 and 272.24 +/- 67.15 microg g(-1) dry mass, respectively), and significantly shorter (p < 0.001) NRR times (10.22 +/- 3.53 and 2.67 +/- 2.83 min, respectively), after 6 weeks, compared to the control group (67.85 +/- 31.08 microg g(-1) dry mass and 24.44 +/- 8.35 min). In both exposure groups NRR times became progressively shorter as body copper concentrations increased over time. Thus, both exposure concentration and exposure time of copper oxychloride were shown to be important factors influencing lysosomal responses (and therefore NRR times) of H. aspersa hemocytes. It was concluded that these responses in this species, as measured by the NRR time assay, could be considered a useful cellular biomarker of stress resulting from exposure to copper oxychloride.

Animals↗

PubMed2000

Effect of single and binary combinations of plant-derived molluscicides on reproduction and survival of the snail Achatina fulica.

The effects of sublethal treatments (20% and 60% of LC(50)/24 h) with plant-derived molluscicides on the reproduction of the giant African snail Achatina fulica were studied. Azadirachta indica oil, Cedrus deodara oil, Allium sativum bulb powder, and Nerium indicum bark powder singly and binary combinations on reproduction and survival of A. fulica were investigated. Repeated treatment occurred on day 0, day 15, and day 30. These plant-derived molluscicides significantly reduced fecundity, egg viability, and survival of A. fulica within 15 days. Discontinuation of the treatments after day 30 did not lead to a recovery trend in the next 30 days. Day 0 sublethal treatment of all the molluscicides caused a maximum reduction in protein, amino acid, DNA, RNA, and phospholipid levels and simultaneous increase in lipid peroxidation in the ovotestis of treated A. fulica. It is believed that sublethal exposure of these molluscicides on snail reproduction is a complex process, involving more than one factor in reducing the reproductive capacity of A. fulica.

Animals↗

PubMed2001

Dorsal and snail homologs in leech development.

As part of an examination of how developmental mechanisms such as axis specification, cell fate specification, and segmentation have evolved, we have cloned homologs of the Drosophila melanogaster genes dorsal and snail from the glossiphoniid leech Helobdella robusta. Sequences from one dorsal-class gene (Hro-dl) and two snail-class genes (Hro-sna1 and Hro-sna2) were identified. Polyclonal antibodies were raised against the most conserved domains of HRO-DL and HRO-SNA1. Nuclear staining appeared for both proteins in mid-embryogenesis, in mesodermal and ectodermal precursors. During segmentation, segmentally iterated stripes of cells with strong HRO-DL staining appeared. The stripes of HRO-DL staining were first concentrated in the cytoplasm of cells, and later in the nuclei. Around this time, HRO-SNA levels also appeared in nuclei in segmentally iterated stripes. The localization of HRO-DL and HRO-SNA proteins raise the possibility that these genes are part of a conserved genetic pathway that, instead of specifying the dorsoventral axis and the mesoderm as in flies, might play a role in the diversification of cell types within segment primordia during leech development.

Amino Acid Sequence↗

PubMed2005

Three-dimensional culture of leech and snail ganglia for studies of neural repair.

Three-dimensional (3D) collagen gels provide a stable matrix in which isolated regenerating ganglia from leech and snail can be maintained for studies of the molecular and cellular mechanisms underlying the regenerative process. Segmental ganglia from leech, or supraoesophageal, suboesophageal or buccal ganglia from snail were maintained for up to 3 weeks in 3D matrices of mammalian Type I collagen. The collagen matrix supports the regenerative outgrowth of axon tracts as well as the migration of microglial cells, important elements in the repair process. Proteins or soluble factors or target tissue may be added to the basic collagen matrix to manipulate the environment of the regenerating tissue. We describe techniques for immunostaining of regenerating axons and microglial cells within the gel matrix in combination with staining of cell nuclei, and the use of intracellular labelling to distinguish axons of identified neurons within the regenerative outgrowth.

Animals↗

PubMed2006

The neuropeptide FMRFamide can protect cells against apoptosis in the snail digestive gland.

FMRFamide-related peptides are widespread neurotransmitters or neurohormones regulating somatic or visceral motor activity. Some recent data indicate that these neuropeptides may be involved in the control of cell proliferation and apoptosis. In this work we investigated the possible effect of FMRFamide on cell viability in an invertebrate-type proliferating tissue. As a model, we used the midintestinal gland of the snail, Helix lucorum Linnaeus. Immunohistochemistry demonstrated the direct innervation of the gland cells by FMRFamide-containing nerve fibers. Midintestinal glands of snails were injected with 50 microM FMRFamide and the control with sterile deionised water or bovine serum albumin (BSA). Injections were administrated 4 times. Transmission electron microscopy, annexin V-labeling, thiazolyl blue (MTT) viability tests and ploidy analyses were carried out to define the viable/dead cell ratio in the tissue samples. FMRFamide increased the MTT-reduction of tissues, reduced the amount of apoptotic nuclei and annexin V-labeled cells. Deionised water or BSA injection induced cell death. Cell cycle analysis revealed that FMRFamide significantly elevated the amount of cells in G0/G1 phase, but did not induce mitosis. We conclude, that the FMRFamide can be a life-signal for cells, protect them from apoptosis without altering mitosis.

Animals↗

PubMedDate not supplied

Genetic variation in two land snails, Cepaea nemoralis and Succinea putris (Gastropoda, Pulmonata), from sites differing in heavy metal content.

Allozyme variation was determined in two land snail species (Cepaea nemoralis and Succinea putris) from four localities in northern Belgium. In each locality we selected a polluted and a nearby, less-polluted, reference plot. We examined whether (i) genetic variability differed between the polluted and reference plots, (ii) populations from polluted plots experienced recent bottlenecks, and (iii) certain allele or genotype frequencies were associated with the pollution. Our results suggest that (i) about 13% of the genetic differentiation in C. nemoralis and 5% in S. putris was due to differences among polluted and reference plots, (ii) polluted and reference plots had comparable levels of genetic variation, but in C. nemoralis observed heterozygosities were higher in polluted plots, (iii) most plots showed significant evidence for recent bottlenecks, irrespective of the degree of pollution, so that bottlenecks seem poor indicators of pollution-induced stress in land snails, and (iv) mutagenic or pollution-induced modifications did not seem to account for new allozyme variants in polluted sites. The observed patterns of genetic variation may be explained by the action of genetic drift, pollution-mediated selection, restricted gene flow, or a combination of these processes.

Alleles↗

PubMed2005

Long-term synaptic facilitation in defensive behavior command neurons in the snail during acquisition of sensitization depends on RNA synthesis.

Experiments on defensive behavior command neuron LP11 in semi-intact common snails preparations were performed to study transcription processes underlying the mechanisms of neuronal plasticity during acquisition of nociceptive sensitization. Application of nociceptive stimuli to the heads of control snails led to increases in neuron membrane excitability, along with biphasic changes in responses to tactile and chemical sensory stimulation--with depressed responses at the short-term stage and facilitation in the long-term stage of sensitization. Acquisition of sensitization after application of the RNA synthesis inhibitor actinomycin D (20 microM) to neuron LP11 led to complete suppression of synaptic facilitation in responses to sensory stimulation in the long-term stage of sensitization, but had no effect on the short-term depression of responses. However, the inhibitor had no effect on changes in membrane excitability in these conditions. Application of actinomycin D 30 min after the end of the sensitization acquisition process (1 h after the process started) had no effect on membrane excitability or synaptic facilitation. It is suggested that the induction of long-term synaptic facilitation in neuron LP11 during acquisition of nociceptive sensitization is dependent on RNA synthesis occurring in a narrow time interval, while changes in membrane excitability during the 2-3 h after acquisition of sensitization and short-term synaptic plasticity are independent of transcription processes.

Action Potentials↗

PubMed2005

In vivo investigation of genome activity and synaptic plasticity of neurons in snails during learning.

The present report describes in vivo investigations of genome activity and its role in the mechanisms forming long-term synaptic plasticity in defensive behavior command neuron LPl1 during the acquisition of nociceptive sensitization by common snails. Transcription processes were recorded using SYTO 16, a specific fluorescent indicator of DNA activity, along with in vivo computer image analysis. Studies in control snails showed that application of nociceptive stimuli to the head led to biphasic changes in the bioelectrical responses of neurons to tactile and chemical stimulation--depression of responses in the short-term stage (during the 1 h after training) and their facilitation during the long-term stage of sensitization (more than 24 h). There were marked increases in fluorescence over the nucleus of the command neuron stained with SYTO 16 at 15-20 min from the start of training, this lasting 4-5 h. Acquisition of sensitization in the presence of the RNA synthesis inhibitor actinomycin D (20 microM) to the neuron led to the complete elimination of changes in fluorescence and synaptic facilitation in the responses of LPl1 to sensory stimulation in the long-term stage of sensitization but had no effect during the short-term stage of sensitization. Actinomycin D given 30 min after the end of acquisition of sensitization (1 h after the start) had no effect on the dynamics of fluorescence or synaptic facilitation. Thus, the acquisition of nociceptive sensitization is accompanied by a rapid (within 15-20 min) activation of the DNA of neuron LPl1 and subsequent (about 1 h) display of long-term synaptic facilitation. Induction of both processes was suppressed by the RNA synthesis inhibitor over a relatively short time period--1 h from the moment at which training started.

Action Potentials↗

PubMed1990

A novel cardio-excitatory peptide isolated from the atria of the African giant snail, Achatina fulica.

An undecapeptide which potentiates the beat of the ventricle in the African giant snail, Achatina fulica Ferussac, was purified from the atria of the snail. Its primary structure was determined to be H-Ser-Gly-Gln-Ser-Trp-Arg-Pro-Gln-Gly-Arg-Phe-NH2. This peptide was found to have excitatory actions not only on the ventricle but also on the penis retractor muscle, the buccal muscle and the identified neurons controlling the buccal muscle movement of Achatina.

Amino Acid Sequence↗

PubMed1991

Purification of achatin-I from the atria of the African giant snail, Achatina fulica, and its possible function.

Achatin-I previously purified from the ganglia of the African giant snail Achatina fulica was isolated from the atria of this snail. Achatin-I appeared to enhance the cardiac activity in two ways; centrally this peptide increased impulse frequency and produced spike broadening of the identified heart excitatory neuron, PON, and peripherally it enhanced amplitude and frequency of the heart beat. Achatin-I showed excitatory actions not only on the heart but on several other muscles.

Amino Acid Sequence↗