Neuromusculature of the ovijector of ascaris suum (Ascaroidea, nematoda): an ultrastructural and immunocytochemical study.

This study used electron microscopy and confocal scanning laser microscopy interfaced with cytochemistry to study neuromuscular interrelationships in the ovijector of Ascaris suum. An extensive nerve plexus with both FaRPergic and non-FaRPergic components extends over the outer surface of the ovijector. The non-FaRPergic component is derived from nerve branches of the ventral nerve cord, whereas the FaRPergic component emanates from two large FMRFamide-immunoreactive neurons. In the vagina vera, most myofibrils are circular in orientation and a number of them divide and run for short distances in longitudinal and diagonal directions, their myofilaments are also orientated in a variety of directions. Parallel nerve fibres run in tracts along the length of the vagina vera with branches that penetrate the muscle layers. The vagina uteri possesses a thicker hypodermis than that of the vagina vera. It appears rich in secretory and phagocytic vesicles and the luminal side is invested with an electron-dense substance. The musculature of the vagina uteri is less well developed than that of the vagina vera, being restricted to circular myofibrils, with an apparent diagonal arrangement of myofilaments. Also, the innervation is less extensive in the vagina uteri with many fibres returning to the vagina vera to rejoin the nerve net and others continuing into the uteri.

Cloning and characterization of a muscle isoform of a Na,K-ATPase alpha subunit (SNaK1) from Schistosoma mansoni.

A cDNA encoding a Na,K-ATPase alpha subunit homologue, designated SNaK1, was isolated from an adult cDNA library of Schistosoma mansoni. The 3.8 kb DNA contained a 3021 bp open reading frame potentially encoding a 1,007 amino acid protein that had an Mr of 111,817 and a pl of 5.48. Homology searches for SNaK1 revealed approximately 70% sequence identity with a variety of Na, K-ATPases from evolutionarily diverse organisms. SNaK1 is predicted to contain 10 transmembrane regions typical of this protein family as well as other conserved domains, such as the phosphorylation site and ATP binding domain. Antibodies raised against an amino terminal peptide detected the protein in membrane preparations of eggs, cercariae and adult males and females, suggesting a general role for SNaK1. The mobility of the protein differed in various life-stages suggestive of post-transcriptional or post-translational modification. Immunolocalization of SNaK1 in sections of adult worms using epifluorescence and electron microscopy, revealed antibody labelling in the subtegumental and peripheral layers. Strong staining was discernible in the peripheral muscle band indicating that SNaK1 plays a central role in muscle contraction in adult parasites and may be the primary target of ouabain action. Staining was also detected in the secretory bodies in sections of ducts in this region and over the RER of the presumed gastrodermis. Immunogold labelling was also localized over neuronal vesicles in axons associated with the peripheral muscle layer.