Biophysical properties of the surface lipid of parasitic nematodes.

The biophysical properties of the surface lipid layer (the epicuticle) of living parasitic nematodes (Trichinella spiralis and Toxocara canis) were examined using fluorescent lipid analogues. A variety of such probes were screened, and only 5-N-(octadecanoyl)-aminofluorescein was found to insert into the outer lipid layer. Fluorescence quenching experiments showed that this probe was confined to the surface, and the rate of its lateral diffusion was then measured by Fluorescence Recovery After Photobleaching. This showed that the probe was not free to diffuse within the plane of the epicuticle. This structure is, therefore, extraordinary in its selectivity to lipid probes, and in the restricted lateral mobility of inserted lipid components.

Biochemical properties of larval excretory-secretory glycoproteins of the parasitic nematode Toxocara canis.

Toxocara canis larvae, infective to Man, secrete a number of antigenic macromolecules into culture medium over prolonged periods of time. These antigens have been collected and characterised with respect to molecular weight by sodium dodecyl sulphate-polyacrylamide gel electrophoresis following extrinsic and intrinsic radiolabelling, or electrophoresis followed by gel staining or immunoblotting. Panels of enzymes and lectins have been applied to examine protease sensitivity and carbohydrate composition, respectively, and a number of other biochemical data have been noted. Taken together, the excretory-secretory molecules contain more than 40% carbohydrate of which the majority is N-acetylgalactosamine and galactose. The individual antigens may readily be separated by gel filtration on a Sepharose 6B column, and it is shown that the major excretory-secretory macromolecules are all glycoproteins which differ in essential characteristics. For example, the 32 kDa antigen (TES-32) binds concanavalin A, is sensitive to a range of proteases and is the band most readily stained by silver and Coomassie blue. Both TES-120 and TES-400 components are resistant to tryptic or peptic cleavage, bind to Helix pomatia lectin and stain with periodic acid-Schiff, yet unlike TES-120, TES-400 does not incorporate radioactive methionine nor can it be stained by silver stain techniques. Finally, one protease, staphylococcal V8, reveals cleavage sites only in the TES-70 and TES-400 molecules.

Metabolite mapping of Toxocara canis using one- and two-dimensional proton magnetic resonance spectroscopy.

One- and two-dimensional proton (1H) nuclear magnetic resonance (NMR) spectroscopic techniques have yielded detailed in vitro profiles of the metabolites present in the parasitic nematode Toxocara canis. The major intracellular metabolites were found to include trehalose, alanine, succinate, acetate, propionate and alpha-glycerophosphorylcholine.

Biochemical polymorphism in Parascaris equorum, Toxocara canis and Toxocara cati.

Vertical starch gel electrophoresis was used to resolve proteins encoded by 18 gene loci in ascaridoid nematodes. Estimates of genetic variability were made from population samples of the dog ascarid (Toxocara canis), cat ascarid (Toxocara cati), and the horse ascarid (Parascaris equorum). Levels of polymorphism and mean heterozygosity were high, which is not consistent with the hypothesis that the intestinal environment selects for monomorphism among endoparasites. Most observed allele frequencies conformed to Hardy-Weinberg equilibrium expectations as tested by chi2 goodness-of-fit, suggesting that the proteins evaluated are inherited in a Mendelian fashion and that these nematodes are mating at random. Subunit structures of the following enzymes, deduced from electrophoretic phenotypes of heterozygotes, corresponded to those of vertebrates: lactate dehydrogenase; malate dehydrogenase; 6-phosphogluconate dehydrogenase; phosphoglucomutase; esterase D; peptidase B; peptidase D; and mannose-6-phosphate isomerase. This observation substantiates the conservative nature of polypeptide subunit number across phylogenetically diverse groups of organisms.

Hemoimmuno-adherence test (HIAT) for the detection of antibodies anti-Toxocara canis L2 larvae.

The use of a hemoimmuno-adherence test (HIAT) for detecting antibodies anti-L2 larvae of Toxocara canis is presented. The HIAT allows to reveal the presence of antibodies in the sera of both naturally and experimentally infected animals. The sensitivity of HIAT appears to be comparable to that of methods such as immunoenzymatic ones.

Activation of complement in C-reactive protein positive sera by phosphorylcholine-bearing component isolated from parasite extract.

Phosphorylcholine-bearing component levels in extracts of various parasites were determined by a capillary precipitin test using anti-phosphorylcholine Ig A myeloma protein. TEPC-15. Phosphorylcholine was demonstrated as a structural component not only in nematodes but also in trematodes and cestodes. The phosphorylcholine-bearing component was isolated from an extract of Toxocara canis larvae using a TEPC-15-Sepharose 4B column. The component reacted with C-reactive protein in sera to form one precipitin line in immunoelectrophoresis. The component provided two Brilliant Coomassie Blue positive bands in SDS-polyacrylamide gel electrophoresis. It reacted with C-reactive protein to activate complement in serum.