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The glycosylation abilities of snails deserve attention, because snail species serve as intermediate hosts in the developmental cycles of some human and cattle parasites. In analogy to many other host-pathogen relations, the glycosylation of snail proteins may likewise contribute to these host-parasite interactions. Here we present an overview on the O-glycan structures of 8 different snails (land and water snails, with or without shell): Arion lusitanicus, Achatina fulica, Biomphalaria glabrata, Cepaea hortensis, Clea helena, Helix pomatia, Limax maximus and Planorbarius corneus. The O-glycans were released from the purified snail proteins by β-elimination. Further analysis was carried out by liquid chromatography coupled to electrospray ionization mass spectrometry and – for the main structures – by gas chromatography/mass spectrometry. Snail O-glycans are built from the four monosaccharide constituents: N-acetylgalactosamine, galactose, mannose and fucose. An additional modification is a methylation of the hexoses. The common trisaccharide core structure was determined in Arion lusitanicus to be N-acetylgalactosamine linked to the protein elongated by two 4-O-methylated galactose residues. Further elongations by methylated and unmethylated galactose and mannose residues and/or fucose are present. The typical snail O-glycan structures are different to those so far described. Similar to snail N-glycan structures they display methylated hexose residues.

Since the discovery of lectins in the 1890s, it has remained a challenge to define the biological function(s). A basic premise of lectin study is that their physiological function(s) relate to their carbohydrate-binding properties. Thus, detailed and useful descriptions of tissue distribution, sugar specificity, and molecular structures are available for many lectins. From the earliest reports, possible roles in fertilization and immune responses have been investigated. Lectins secreted from the albumin gland of the snail Helix pomatia able to agglutinate erythrocytes (Camus, 1899) were later named “protectins” to suggest that these protect against microbial or fungal infection (Prokop, 1965). Studies on arthropod species, such as the horseshoe crab Limulus polyphemus, the lobster Homarus americanus,the crab Eupagurus prideauxii, and the spider crab Maia squinado, extended the hemagglutination properties to hemolymph lectins, providing evidence that expression of these proteins is inducible by challenge with agglutinated bacteria, and furthermore that the induced lectins have opsonic properties (Cantacuzene, 1919).

When compared to vertebrate nervous systems, invertebrate ganglia are studied easily because of several technical advantages. The relative simplicity of these ganglia enabled e.g. the study of the ionic bases of bioelectrical activity of neurons and the study of mechanisms underlying learning and memory. Furthermore, there are several examples of oscillatory events in invertebrate nervous systems which are well understood on the single neuron level (cf. Kandel, 1976; Fentress, 1976). Thus, the buccal ganglia of snails which are part of the snail central nervous system contain a neuronal generator of the motor program for food intake i.e. for biting and swallowing. The generator is spontaneously active even when the ganglia are isolated from the animal. The physiologic oscillatory activity of this generator has been studied in several snail species (cf. Siegler, 1977; Bulloch and Dorsett, 1979; Benjamin and Elliott, 1989).

A model for the impulse transmission between nerve cells is presented. The model is compared with experiments on nerve cell bodies of the large land snail Helix pomatia. Synaptic input is simulated by equal-sized square current pulses applied at a constant rate. The output pattern consists of a mixture of spikes and dropouts, where the response fraction depends on stimulus strength and frequency in a non-trivial manner. In the periodic model, the output locks to the input at simple ratios (1:1, 2:1, 3:2, etc.) resulting in the fractal relation called the “Devil’s staircase” between response fraction and stimulation strength or rate. In the chaotic model the near-threshold behavior of the nerve cell is included, resulting in a breakdown of the staircase into a mixture of regions with regular behavior and regions with chaotic behavior. In the chaotic regions, the mean output frequency differs from the mean frequency of nearby regions. The behavior of this model is close to the behavior of the nerve cell. Coupling is mimicked by applying the output from one cell to another cell with the same model parameters. Even in very simple systems, the resulting output depends not only on the strength of the coupling, but also on the precise timing of the incoming impulses. The signal processing of a nerve cell is therefore not just a function of the mean firing frequency. It is a result of subtly timed mixtures of regular and chaotic firing patterns.

When the original report by Hodgkin and Huxley was published in 1952, the two-channel model of nerve excitability derived from the squid giant axon was expected to explain the electrical properties of many nerve cells as well as those of their respective axons, cell bodies, dendrites, and terminals. During the past 15 years, this model has been superseded by the discovery of several voltage-gated ionic conductances, particularly for potassium and calcium.

The phylum of Mollusca includes a large number of species which are extremely varied in body shape and size. The molluscs are generally known for their soft body, but above all for having a characteristic shell; although, in fact, many species exist which do not have one.

Conceptually, the basic mechanism common to both vertebrate and invertebrate immune systems is the recognition of and reaction against invading nonself materials and neoplastic cells. The information available on vertebrate immune systems has firmly established that both cell-mediated and humoral immune mechanisms occur. Furthermore, the cooperative effects of three classes of circulating leukocytes, namely B lymphocytes, T lymphocytes, and the highly phagocytic macrophages, are operative. The remarkable fact that has become evident from studies on vertebrate immune phenomena is that reactions against foreignness, involving the three mentioned cell types, exhibit a great deal of molecular specificity owing to the presence of antigen-specific receptors on the surfaces of both B and T lymphocytes.

In the course of our investigations on the anti-neuraminyl-specificity of the hemagglutinin from the hemolymph of the horseshoe crab Limulus polyphemus (Cohen et al., 1972; Cohen, 1968), we included the hemolymph of this living fossil also in our experiments, dealing with the occurrence and distribution of blood group A like active structures in nature as detected by the heterophile anti-N-acetyl-D-galactosamine agglutinin/precipitin from the albumin gland of the snail Helix pomatia (see Prokop et al., 1974).

In 1970 Campbell and Bishop, describing the nitrogen metabolism in Moluscs, had written: “Terrestrial snails might thus serve as useful systems for investigating the specific derangements present in persons exhibiting the Lesch-Nyhan Syndrome” (1). For several years we have been concerned with the purine-nucleotide metabolism in land snail Helix pomatia (Pulmonata). This gastropod has been found to be purinotelic (11). During winter sleep, H. pomatia accumulates uric acid, which accounts for 75 % of the total purine content in the nephridium at the end of hibernation. During its active life, the nephridial excreta contain uric acid, xanthine and guanine, accounting for 34 – 49, 34 – 55 and 11 – 16 %, respectively of the total amount of purines excreted (12). An enzymic system allowing under normal, physiological conditions such diversity of the end-products of the nitrogen metabolism looked very promising. On the basis of investigations of the enzymes participating in the purine-nucleotide metabolism in the hepatopancreas, which is an organ homologous to the liver of Vertebrates, the scheme presented in Fig. 1. is suggested.

In biological systems the information is coded in terms of the interval between successive action potentials.

In ADCC, recognition of the target cells is mediated by IgG antibodies. Available evidence also suggests that target cell lysis is triggered by the interaction of Fc structures of the inducing IgG with the Fcγ-receptors of the killer cell (1). Target cell recognition and triggering of lysis would thus appear to be linked but independent reactions. In the following I will discuss some additional recognition phenomena which are independent of the inducing antibody but which nevertheless are important in regulating killer cell — target cell interaction ADCC. We call this “associative recognition” and I will discuss four examples, three from our own work and one from the work of others.

α-N-Acetylgalactosaminidase is an unusual lysosomal glycosidase in that no genetic abnormality involving this enzyme has been discovered. It was discovered many years ago, when Freudenberg and Eichel (1) found that extracts of the hepatopancreas from the snail Helix pomatia inactivated blood group A substance with the release of N-acetylhexosamine and galactose. Cell-free extracts of the flagellate Trichomonas foetus were also observed to contain activity that destroyed blood group A-active glycoprotein (2). Subsequent studies with partially purified preparations from these sources indicated that the loss of serological activity was accompanied by the concomitant liberation of terminal N-acetylgalactosamine (GalNAc) residues (3,4). Terminal GalNAc residues were also released from desialized sheep submaxillary mucin by enzyme fractions from various animal sources (5–7) and Clostridium perfringens (8).

AMP-deaminase (EC 3.5.4.6) has been known for several years as a main source of ammonia liberated in the skeletal muscle of higher vertebrates. Skeletal muscle is the richest source of AMP-deaminase, and molecular properties as well as regulation of the reaction catalyzed by muscle deaminases were carefully studied and described.2–7

Calcium activated membrane permeabilities appear usually as a consequence of calcium currents. To correlate the dynamics of Ca-entry with its effects one would wish to have a measure of steady state and transient changes of intracellular free Ca ([Ca]i). Estimates by various methods suggest that the resting level of [Ca]i is at least 5 orders of magnitude lower than the value expected from a passive distribution (for review see Ashley and Campbell, 1979). Even if the increase in [Ca]i during excitation is small in absolute terms, it may be a large relative change compared to the low background level and may have an important messenger function.

Snail galactans are highly branched polysaccharides which are synthesized in the albumen glands of pulmonate and prosobranchiate snails and added to the perivitelline fluid of their eggs as nutritive material for the growing embryos. (1) Snail galactans are predominantly composed of D Galactose linked glycosidically l→3 and l→6 (2,3). Depending on the species additional constituents were described, such as Lgalactose in Helix pomatia, Arianta arbustorum or Capaea nemoralis (14%), L fucose in Ampullarius spec. (2%) (4) or phosphate groups as in H. pomatia, C. nemoralis and in Biompholario glabrata (2%) (3).

The change of the biological membrane permeability is considered to be one of the earliest effects of ionizing radiation /IR/.1 Nevertheless, the radiation disturbance mechnisms of the systems regulating the ions homeostasis /including the main monovalent cations — sodium and potassium/ have not been investigated yet. Studies of these effects are of great interest, especially for the nerve tissue, taking into consideration the interpreting of the neurologic disturbance development mechanisms in the case of radiation pathology. In connection with this, the IR action mechanisms on the transport systems of Na+ and K+ in the model experiments on the giant neurons of Helix pomatia were investigated.

Lately, it has become more and more evident that in the regulation of the molluscan heart one has to deal with more than a single excitatory factor; as in the process of excitatory effects, a chain-like reaction of several different factors is involved. The data that reported the existence of several cardio-accelerators in the nervous system of gastropods (Kerkut and Laverack 1960; Jaeger 1966; Cottrell 1966; Welsh and Frontali 1966; S.-Rozsa and Zs.-Nagy 1967) have already indicated that for the realization of excitatory effects on molluscan heart more than a single excitatory transmitter is responsible.

Mixtures of pure estrogens and many of their derivatives, such as the 3-methyl ethers, the acetates, the trifluoracetates and the TMS ethers, have been successfully analyzed by GLC using a variety of stationary phases (1–5). However, analysis of estrogens in the urine of non-pregnant women by this technique presents particular difficulties due to the fact that these compounds are excreted in a concentration which is very low in relation to the amounts of interfering substances. The need of extensive purification of urinary extracts before analysis of estrogens by GLC has been emphasized by Wotiz and Chattoraj (6).