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At least 109 records · Page 6Linked to original sources
PubMed1999

Blocking of the axon spikes by pentylenetetrazol in an identified neuron of the snail Helix lucorum, with consequent induction of epileptic activity in the cell body of the same neuron.

In an isolated preparation which consists of the buccal ganglia and the salivary nerve of Helix lucorum, neuron B2 can be identified by simultaneously recording the soma spike intracellularly and the axon spike extracellularly from the peripheral salivary nerve. The convulsant drug pentylenetetrazol (PTZ) eliminates the axon spike of the neuron within 1-5 min after its application while epileptic activity is induced in the soma of the same neuron for hours. It is interesting that almost all nerve activity in the peripheral nerve is blocked by PTZ.

Action Potentials↗
PubMed1981

Reassembly of wall domains of Roman-snail (Helix pomatia) beta-haemocyanin.

beta-Haemocyanin molecules consist of 20 very large polypeptide chains. These chains are composed of eight structural domains. So-called 'collar' domains can be removed by trypsinolysis of the native cylindrical molecule, resulting in an association of the remaining hollow cylinders into large tubular polymers. Dissociation of the tubular polymers gives one single- and four multi-domain fragments. The role of these fragments in the reassembly process of these tubular polymers was investigated. The two-domain fragment could form tubular polymers. The other domain fragments were not able to form tubular polymers unless in the presence of the two-domain fragment. Tubular polymers with enlarged diameter and ribbon-like structures were observed in the reassembly products when the one-domain fragment was omitted.

Animals↗
PubMed1988

The reaction of hydroxyurea with oxyhaemocyanin and methaemocyanin of the crayfish Astacus leptodactylus and the snail Helix pomatia.

The reaction of hydroxyurea with the oxyhaemocyanins of Astacus leptodactylus and Helix pomatia yielded methaemocyanins which could be regenerated with hydroxylamine. Hydroxyurea did not react with Astacus methaemocyanin, but quantitatively regenerated Helix methaemocyanin under N2. The reaction of hydroxyurea with Helix haemocyanin at pH 5.7 under air thus led to a steady state, with an oxyhaemocyanin/methaemocyanin ratio of 2.05:1.

Animals↗
PubMed1989

The reaction of nitrogen monoxide with the haemocyanins of the crayfish Astacus leptodactylus and the snail Helix pomatia.

The rate of the reaction of Astacus leptodactylus methaemocyanin with NO follows the Henderson-Hasselbalch equation with a pKa of 5.85, suggesting that one imidazole ligand of Cu was exchanged for NO. The reaction is blocked by F- as a bridging ligand. The same imidazole residue might be responsible for the decomposition of nitrosylhaemocyanin, [Cu1NO+CuII], with an unlocated binding site for NO, into methaemocyanin and NO, as the rate increase with pH. NO could react preferentially with CuA of Helix pomatia methaemocyanin, CuA'IICuBII, as it possibly has only two histidine ligands instead of the three of CuA in Astacus haemocyanin. This difference might explain the higher formation rate and the much greater stability of Helix nitrosylhaemocyanin. The fast reaction is governed by a pKa of 6.80, probably of a bridging mu-aquo ligand. With F- or a mu-hydroxo bridging ligand a low reaction rate was still observed, in contrast with Astacus methaemocyanin. Helix nitrosylhaemocyanin was transformed by N3- into methaemocyanin with the liberation of N2 and N2O. This methaemocyanin could almost quantitatively be regenerated with H2O2. Helix nitrosylhaemocyanin was only partially regenerated by a direct treatment with H2O2 and almost quantitatively by HONH2 in a similar fairly fast reaction, followed by a much slower one.

Animals↗
PubMed2001

Evolution of genetic variability in a population of the edible snail, Helix aspersa Müller, undergoing domestication and short-term selection.

The evolution of genetic variability is studied in six successive generations of a population originating from wild Helix aspersa. During the first three generations (G1 to G3), no artificial selection was applied. During the next three generations (G4 to G6), two lines were reared: a control line (C) and a line (S) selected for increased adult weight. Genetic variability is described by genealogical parameters (inbreeding, number of founders, effective number of founders and ancestors, effective number of remaining genomes) and by the additive genetic variance in adult weight. A large decrease in all parameters was observed between G1 and G2, suggesting strong natural selection: additive genetic variance in adult weight (transformed data) decreased from 0.0119 +/- 3.8 x 10(-3) to 0.0070 +/- 1.7 x 10(-3) (P < 0.05) and effective number of ancestors from 97.4 to 67.0. Selection also caused a large decrease during the first generation: additive genetic variance was 0.0079 +/- 2.1 x 10(-3) in G3 and 0.0040 +/- 1.1 x 10(-3) after the first selection cycle (P < 0.02). At the same time, the effective number of ancestors decreased from 59.2 to 29.5 and 24.2. This decrease is consistent with the theory of selection and the Bulmer effect.

Animals↗
PubMed2001

Evolutionary history of the land snail Helix aspersa in the Western Mediterranean: preliminary results inferred from mitochondrial DNA sequences.

Intraspecific phylogeographic methods provide a means of examining the history of genetic exchange among populations. As part of a study of the history of Helix aspersa in the Western Mediterranean, we performed a phylogenetic analysis based on partial sequences of the mitochondrial large ribosomal subunit (16S) gene. Our samples include 31 H. a. aspersa populations from North Africa previously investigated for anatomical and biochemical characters. To clarify subspecific relationships, three individuals of the subspecies H. a. maxima were also studied. The molecular phylogeny inferred agrees largely with previous results, in splitting H. a. aspersa haplotypes into an eastern and a western group. H. a. maxima haplotypes form a third lineage arising before the H. a. aspersa groups. Divergence times estimated between the lineages suggest that dispersal during Pleistocene glaciation and vicariance events due to Pliocene geological changes in the western Mediterranean may both have played a significant part in the establishment of the present range of H. aspersa.

Animals↗
PubMed1992

Distribution of alpha CDCP-immunoreactive neurons in the central nervous system of the snail Helix aspersa.

alpha CDCP is a neuropeptide produced by the caudodorsal cells of Lymnaea stagnalis and encoded by the genes of the egg-laying hormone (ELH). The use of a polyclonal antiserum raised against alpha CDCP resulted in the detection of about 800 immunoreactive neurons in the parietal ganglia and a small population (60 cells) in the cerebral ganglia of Helix aspersa. As the genes of ELH are well conserved among the gastropod species, these data designate the parietal ganglia as a putative source for the egg-laying hormone in Helix aspersa.

Amino Acid Sequence↗