Chemotaxonomical investigations on the occurrence of sialic acids in protostomia and deuterostomia

Opsonic function of sialic acid specific lectin in freshwater crab Paratelphusa jacquemontii

The sialic acid specific humoral lectin, Pjlec of the freshwater crab Paratelphusa jacquemontii was investigated for its opsonin function with rabbit erythrocyte as target cell for phagocytosis by the crab's hemocyte. The untreated or trypsin treated erythrocyte induced lectin response after challenge however failed when treated with neuraminidase evidently indicating glycan dependency for elicited immune response. Our observation of in vitro phagocytosis of the erythrocyte untreated or coated with serum, clarified serum appeared to be recognized and engulfed by hemocytes but when coated with isolated lectin Pjlec, the response was elicited. Moreover, with trypsin treated erythrocyte the response remained unchanged but neuraminidase or O-glycosidase treatment eliminated the response reaction. This suggested the sialic acid specific reaction of lectin with the erythrocyte and was essential for recognition to allow the lectin Pjlec to act as an opsonin. The flowcytometry observation affirmed the enhancement of phagocytosis by Pjlec coated hemocyte. The efficiency of in vitro hemolysis of Pjlec coated erythrocyte with hemocyte when compared to untreated erythrocyte with or without hemocyte also established the opsonic function of the lectin. The mechanism of phagocytosis and induction were dependent on specific recognition of the erythrocyte by the multivalent binding site of the lectin protein, and the elicitation of the immune response was a function of the sialoglycan surface. The pathway of the challenge suggested that after entry of nonself recognition by lectin was followed by induction and activation of phagocytosis by opsonic binding of the lectin.

Animal phylogeny and the ancestry of bilaterians: inferences from morphology and 18S rDNA gene sequences

Insight into the origin and early evolution of the animal phyla requires an understanding of how animal groups are related to one another. Thus, we set out to explore animal phylogeny by analyzing with maximum parsimony 138 morphological characters from 40 metazoan groups, and 304 18S rDNA sequences, both separately and together. Both types of data agree that arthropods are not closely related to annelids: the former group with nematodes and other molting animals (Ecdysozoa), and the latter group with molluscs and other taxa with spiral cleavage. Furthermore, neither brachiopods nor chaetognaths group with deuterostomes; brachiopods are allied with the molluscs and annelids (Lophotrochozoa), whereas chaetognaths are allied with the ecdysozoans. The major discordance between the two types of data concerns the rooting of the bilaterians, and the bilaterian sister-taxon. Morphology suggests that the root is between deuterostomes and protostomes, with ctenophores the bilaterian sister-group, whereas 18S rDNA suggests that the root is within the Lophotrochozoa with acoel flatworms and gnathostomulids as basal bilaterians, and with cnidarians the bilaterian sister-group. We suggest that this basal position of acoels and gnathostomulids is artifactal because for 1,000 replicate phylogenetic analyses with one random sequence as outgroup, the majority root with an acoel flatworm or gnathostomulid as the basal ingroup lineage. When these problematic taxa are eliminated from the matrix, the combined analysis suggests that the root lies between the deuterostomes and protostomes, and Ctenophora is the bilaterian sister-group. We suggest that because chaetognaths and lophophorates, taxa traditionally allied with deuterostomes, occupy basal positions within their respective protostomian clades, deuterostomy most likely represents a suite of characters plesiomorphic for bilaterians.

Articulated halkieriids from the Lower Cambrian of North Greenland and their role in early protostome evolution

Articulated halkieriids ofHalkieria evangelistasp. nov. are described from the Sirius Passet fauna in the Lower Cambrian Buen Formation of Peary Land, North Greenland. Three zones of sclerites are recognizable: obliquely inclined rows of dorsal palmates, quincuncially inserted lateral cultrates and imbricated bundles of ventro-lateral siculates. In addition there is a prominent shell at both ends, each with radial ornamentation. Both sclerites and shells were probably calcareous, but increase in body size led to insertion of additional sclerites but marginal accretion of the shells. The ventral sole was soft and, in life, presumably muscular. Recognizable features of internal anatomy include a gut trace and possible musculature, inferred from imprints on the interior of the anterior shell. Halkieriids are closely related to the Middle CambrianWixaxia, best known from the Burgess Shale: this clade appears to have played an important role in early protostome evolution. From an animal fairly closely related toWixaxiaarose the polychaete annelids; the bundles of siculate sclerites prefigure the neurochaetae whereas the dorsal notochaetae derive from the palmates.Wixaxiaappears to have a relic shell and a similar structure in the sternaspid polychaetes may be an evolutionary remnant. The primitive state in extant polychaetes is best expressed in groups such as chrysopetalids, aphroditaceans and amphinomids. The homology between polychaete chaetae and the mantle setae of brachiopods is one line of evidence to suggest that the latter phylum arose from a juvenile halkieriid in which the posterior shell was first in juxtaposition to the anterior and rotated beneath it to provide the bivalved condition of an ancestral brachiopod.H. evangelistasp. nov. has shells which resemble those of a brachiopod; in particular the posterior one. From predecessors of the halkieriids known as siphogonuchitids it is possible that both chitons (polyplacophorans) and conchiferan molluscs arose. The hypothesis of halkieriids and their relatives having a key role in annelid—brachiopod—mollusc evolution is in accord with some earlier proposals and recent evidence from molecular biology. It casts doubt, however, on a number of favoured concepts including the primitive annelid being oligochaetoid and a burrower, the brachiopods being deuterostomes and the coelom being an archaic feature of metazoans. Rather, the annelid coelom arose as a functional consequence of the transition from a creeping halkieriid to a polychaete with stepping parapodial locomotion.

Purification and characterization of N-glycolyneuraminic-acid-specific lectin from Scylla serrata

A sialic-acid-binding lectin with specificity for N-glycolylneuraminic acid (NeuGc) was purified from the hemolymph of the marine crab Scylla serrata by affinity chromatography using thyroglobulin-coupled agarose. The binding specificity of Scylla lectin distinguishes it from other known sialic-acid-specific lectins found in Limulus polyphemus and Limax flavus, which show a broader range of specificity for sialic acids. The molecular mass of the purified lectin is about 55 kDa. Under reducing conditions (SDS/PAGE), it resolved into two subunits of 30 kDa and 25 kDa. NeuGc inhibited hemagglutination activity of the purified lectin at a concentration as low as 0.6 mM, whereas N-acetylneuraminic acid (NeuAc) even at a concentration of 100 mM, failed to inhibit hemagglutination. This finding was supported by potent inhibition of hemagglutination by bovine and porcine thyroglobulins, which contain a NeuGc alpha 2-6Gal as terminal component of oligosaccharide residues. Neither glycoproteins (glycophorin NN; porcine submaxillary mucin), which contain NeuAc alpha 2-3Gal/GalNAc and NeuAc alpha 2-6GalNAc, nor human acid glycoprotein, which contains NeuAc alpha 2-3/alpha 2-6 Gal, or colominic acid, a sialopolymer with NeuAc alpha 2-8NeuAc, inhibited the lectin activity. The specificity of the lectin for NeuGc appears to account for the fact that it agglutinates rabbit and mice erythrocytes, but not human A, O, AB, rat or chicken erythrocytes, which contain NeuAc. The inability of the lectin to agglutinate erythrocytes (horse) that prominently express NeuGc could be due to O-acetylation of NeuGc. In support of this, bovine submaxillary mucin, which contains O-acetylated NeuGc inhibited the hemagglutination of the lectin better after removal of O-acetyl groups by base treatment. The unique specificity of Scylla lectin is of diagnostic potential for human cancer tissues expressing NeuGc, since NeuGc is not found in normal human tissues.

Evidence that ruthenium red disturbs the synaptic transmission in the rat hippocampal slices through interacting with sialic acid residues

Ruthenium red (RR) at a concentration of 0.71 mM selectively blocked synaptic transmission in hippocampal slices. Antidromically evoked potentials and fibre potentials were only little affected. The action of RR was reversible by washout, but only following shorter (40-50 min) times of incubation. After longer incubation times (hours), the abolished population spike did not recover after washout but could be restored by facilitation of the calcium transport into the nerve terminal with 3,4-diaminopyridine. Partial liberation of sialic acid with neuraminidase from Vibrio Cholerae markedly increased the time after which the potential was abolished by RR. Exogenously added gangliosides and sialic acid also delayed the action of RR. Calcium at a concentration of 13.2 mM prevented or reduced the RR effect. It is concluded that RR binds to sialic acid residues, interfering with neurotransmission by disturbing the calcium transport into the cell.

Brain gangliosides in monotremes, marsupials and placentals: phylogenetic and thermoregulatory aspects

The concentration and composition of brain gangliosides of 17 mammalian species belonging to the subclasses of Prototheria (monotremes), Metatheria (marsupials), and Eutheria (placentals) were investigated. The mean concentration of brain gangliosides ranges from 525 to 610 micrograms NeuAc/g wet wt in monotremes, 445-900 micrograms in marsupials and from 630 to 1130 micrograms in the placentals. In the phylogenetic series of mammals, a decrease in the complexity of brain ganglioside composition becomes obvious: a drastic reduction in the number of individual ganglioside fractions particularly those of the c-pathway of biosynthesis, took place from the level of monotremes to that of the marsupials and placentals. In monotremes, marsupials and "lower" placentals (insectivores) the percentage of alkali-labile gangliosides is relatively low (between traces and 5%), whereas in the higher evolved mammals it amounts to about 20% of all gangliosides. The ratio of the contents of the two major mammalian ganglioside fractions GD1a and GT1b is generally in the range of 1.0 and even higher; in the heterothermic platypus from the monotremes and in hibernators among the placental mammals, however, it is much lower (about 0.8). These data support the hypothesis that the brain ganglioside composition not only depends on the phylogenetic level of nervous organization (cephalization) but is additionally correlated with the state of thermal adaptation.

Lipids of nervous tissue: composition and metabolism

As indicated in the Introduction, the many significant developments in the recent past in our knowledge of the lipids of the nervous system have been collated in this article. That there is a sustained interest in this field is evident from the rather long bibliography which is itself selective. Obviously, it is not possible to summarize a review in which the chemistry, distribution and metabolism of a great variety of lipids have been discussed. However, from the progress of research, some general conclusions may be drawn. The period of discovery of new lipids in the nervous system appears to be over. All the major lipid components have been discovered and a great deal is now known about their structure and metabolism. Analytical data on the lipid composition of the CNS are available for a number of species and such data on the major areas of the brain are also at hand but information on the various subregions is meagre. Such investigations may yet provide clues to the role of lipids in brain function. Compared to CNS, information on PNS is less adequate. Further research on PNS would be worthwhile as it is amenable for experimental manipulation and complex mechanisms such as myelination can be investigated in this tissue. There are reports correlating lipid constituents with the increased complexity in the organization of the nervous system during evolution. This line of investigation may prove useful. The basic aim of research on the lipids of the nervous tissue is to unravel their functional significance. Most of the hydrophobic moieties of the nervous tissue lipids are comprised of very long chain, highly unsaturated and in some cases hydroxylated residues, and recent studies have shown that each lipid class contains characteristic molecular species. Their contribution to the properties of neural membranes such as excitability remains to be elucidated. Similarly, a large proportion of the phospholipid molecules in the myelin membrane are ethanolamine plasmalogens and their importance in this membrane is not known. It is firmly established that phosphatidylinositol and possibly polyphosphoinositides are involved with events at the synapse during impulse propagation, but their precise role in molecular terms is not clear. Gangliosides, with their structural complexity and amphipathic nature, have been implicated in a number of biological events which include cellular recognition and acting as adjuncts at receptor sites. More recently, growth promoting and neuritogenic functions have been ascribed to gangliosides. These interesting properties of gangliosides wIll undoubtedly attract greater attention in the future.(ABSTRACT TRUNCATED AT 400 WORDS)

Histochemical detection of anionic components in the cephalopod brain

Brains obtained from three species of mediterranean cephalopods (Loligo, Sepia, Octopus) were fixed in Bouin's solution. Paraffin sections were cut sequentially at the frontal plane and used for Alcian blue staining (critical electrolyte concentration method), colloidal iron hydroxide staining procedure, the periodic acid Schiff's reagent method, and the lead tetra-acetate-Schiff method. The stained sections were evaluated at 2 regions of different histological composition: the palliovisceral ganglion and the optic lobe. A high concentration of anionic components was found in synaptic regions of the neuropil whereas neuronal cell bodies showed a relatively weak staining of these constituents. There was a significant reaction of the perineuronal glia nets in the cellular rind of the palliovisceral ganglion. From the comparison of staining patterns obtained with the 4 methods in this study and literature data it can be concluded that the detected anionic sites are mainly carboxyl groups of acidic proteins and/or glycoproteins. Sulphate groups may be present in lower concentrations. Their distribution reveals that the role of anionic components other than sialic acids in the invertebrate brain might be discussed in the context of synaptic transmission similar to that in vertebrates. The possible involvement of the glia cell population has to be taken into consideration.

Calcium binding sites of synaptosomes from insect nervous system as probed by trivalent terbium ions

Terbium binding to synaptosomes from the central nervous system of the locust was studied by fluorescence spectroscopy and electron microscopy. The protein-sensitized fluorescence of terbium was used to characterize the calcium binding sites of synaptosomes. As judged by electron microscopy and x-ray analysis, terbium ions produced electron-dense patches in regular arrays on the outer surface of synaptosomal membranes and induced marked aggregation of synaptic vesicles in isolated terminals.

Lipid composition in ganglia of Mollusca

The aim of the present study is to ascertain lipid composition in the ganglia of Mollusca. Nervous ganglia in the periesophageal ring dissected from Helix pomatia, Lymnaea stagnalis, Murex trunculus and Murex brandaris were studied by biochemical and histochemical procedures. Glycosphyngolipids are present mainly as sulpholipid; sialic acid and gangliosides are not present as revealed by Svennerholm's reaction and TLC separation. The phospholipid/cholesterol ratios are: 0.47 (Helix), 0.42 (Lymnaea), 0.86 (Murex brandaris) and 1.01 (Murex trunculus).