The function of the intestine in the pulmonate mollusc Helix pomatia L.

Summary Everted sacs of intestine from Helix pomatia do not actively transfer glucose, galatose, methionine, alanine, asparagine, aspartic acid or proline from the mucosal to serosal surfaces. The principal function of the intestine appears to be the reabsorption of water.The study was partly financed through a Reading University Research Board Scholarship. I thank Profs A. Graham, K. Simkiss, J. Machin and Dr C. Kyriakides for their advice and criticisms and E. Snowden and J. Counden for technical assistance.     

Methionine enkephalin inhibits the bursting activity of the Br-type neuron in Helix pomatia L

The present study demonstrates that methionine enkephalin can inhibit the normal bursting activity pattern of the RPal or Br-type neuron and this inhibition can be blocked by prior treatment with naloxone, the selective opiate antagonist. The study demonstrates indirectly the presence of opiate-like receptors in Helix pomatia.     

In vitro biosynthesis of octopamine by the nervous system and the heart of the mollusc gastropode Helix pomatia (author's transl)]

The tyrosine is decarboxylated in vitro by the central nervous tissue and by the intracardiac nervous tissue of Helix pomatia by aromatic amino-acid decarboxylase. The tyramine obtained is then partially transformed into octopamine by tyramine-beta-hydroxylase. The inhibition of monoamine oxidase favours apparition of the 2 amines. The monoamine oxidase seems able to regulate their synthese and to assure their inactivation.     

Organization of the multifunctional neural network regulating visceral organs inHelix pomatia L (Mollusca,Gastropoda)

Summary InHelix pomatia L. the overlapping neuronal network was found to regulate the visceral functions (e.g. cardiorenal, respiratory and genital functions). The neural network is organized around the multifunctional interneurons, which take part in forming both afferent and efferent pathways. The interneurons are sensitive to a wide range of neurotransmitters or transmitter candidates including low molecular weight substances (ACh, 5HT, DA, octopamine, glutamate) and several oligopeptides. In this system both selection of information and modification of membrane properties (for example habituation) are carried out by a combination of simultaneously liberated active agents.     

Multiple prismatic calcium phosphate layers in the jaws of present-day sharks (Chondrichthyes; Selachii)

Summary Jaws of large individuals, over 2 m in total length, of the shark speciesCarcharodon carcharias (great white shark) andIsurus oxyrinchus (mako shark) of the family Lamnidae, andGaleocerdo cuvieri (tiger shark) andCarcharhinus leucas (bull shark) of the family Carcharhinidae were found to have multiple, up to five, layers of prismatic calcium phosphate surrounding the cartilages. Smaller individuals of these species and other known species of living chondrichthyans have only one layer of prismatic calcium phosphate surrounding the cartilages, as also do most species of fossil chondrichthyans. Two exceptions are the fossil shark generaXenacanthus andTamiobatis. Where it is found in living forms, this multiple layered calcification does not appear to be phylogenetic, as it appears to be lacking in other lamnid and carcharhinid genera and species. Rather it appears to be functional, only appearing in larger individuals and species of these two groups, and hence may be necessary to strengthen the jaw cartilages of such individuals for biting.