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At least 253 records · Page 14Linked to original sources
PubMed1981

A novel phosphagen phosphotransferase in the plerocercoids of Schistocephalus solidus (Cestoda: Pseudophyllidea).

Neither phosphagens nor phosphagen phosphotransferase activity could be detected in Fasciola hepatica, Hymenolepis diminuta, Moniezia expansa or in the plerocercoids of Ligula intestinalis. The plerocercoids of Schistocephalus solidus, however, possess an active taurocyamine phosphotransferase, although it too contains no detectable phosphagens. The taurocyamine phosphotransferase of S. solidus has an absolute requirement for a divalent metal ion and ATP could not be replaced by ITP, GTP, CTP or UTP as the phosphate donor. The role of phosphagens in helminths is discussed.

Adenosine Triphosphate↗
PubMed1976

Parasitic helminths of the American avocet Recurvirostra americana: four new species of the families Hymenolepididae and Acoleidae (Cestoda: Cyclophyllidae).

Records are presented of 11 species of parasitic helminths recovered from 37 American avocets. Birds were collected in Kansas and Colorado from April 1973 to August 1974. Parsites found included 3 trematodes, 2 nematodes, 1 acanthocephalan and 5 cestodes, 4 of which are new species. Hymenolepis cervotestis sp.n. (Hymenolepididae) is described from the small intestine of 7 avocets. It exhibits extreme protandry with the testes appearing before external segmentation is evident. Sobolevicanthus coloradensis sp.n. (Hymenolepididae) is described from the small intestine of 4 avocets. This species is found to have its scolex embedded in the intesttinal mucosa of its host. Diorchis recurvirostrae sp.n. (Hymenolepididae) is described from specimens recovered from the small intestine of 5 avocets. Diplophallus coili sp.n. (Acoleidae) is described from the small intestine of all 37 avocets. The family Diploposthidae is suppressed and the family Acoleidae is emended to include the 4 genera previously placed in Diploposthidae. A key to the genera of Acoleidae is presented.

Animals↗
PubMed1986

The seasonal occurrence of Trilocularia acanthiaevulgaris (Cestoda: Tetraphyllidea) from spiny dogfish in the Irish Sea.

Trilocularia acanthiaevulgaris occurs in the stomach and spiral valve of the spiny dogfish. Statistical analyses show that the stomach and spiral valve worms of male fish and the stomach worms of female fish exhibit seasonal trends in prevalence and mean worm burden, with peaks occurring in May, June and July of each year. Spiral valve worms of female fish do not show this trend. Calculation of the product-moment correlation coefficient shows that the peak in the number of stomach worms occurs approximately 1 month before that of spiral valve worms in male fish. Strobilization of the adult spiral valve worms and development of the resulting free proglottides is also seasonal, and takes place in June/July in both sexes. Seasonal trends in prevalence, mean worm burden and maturation of T. acanthiaevulgaris may be related to water temperature, and the cyclical changes in levels of reproductive hormones and thyroid activity associated with migration and mating of spiny dogfish. It is suggested that the availability of infected intermediate hosts and diet of the dogfish may also be important in explaining the seasonality of infection.

Animals↗
PubMed1976

Evasion of the haemocytic defence reaction of certain insects by larvae of Hymenolepis diminuta (Cestoda).

Larvae of Hymenolepis diminuta develop in the haemocoele of the beetles Tribolium and Tenebrio, and of the locust Schistocerca gregaria, without being encapsulated by haemocytes. The mechanism of this evasion of the haemocytic defence reaction has been examined using various techniques. Larvae grown in culture and injected into S. gregaria have a few or no haemocytes adherent even after 8h, although latex beads injected at the same time have been thickly encapsulated. This, and results of transplanting cysticercoids and host tissue between different insect species, suggests that the surface of the larvae may bear an inherent similarity to the surface of host tissues and thus escape recognition as 'not-self' by the host's haemocytes.

Animals↗
PubMed1990

Regulation of macrophage-mediated larvicidal activity in Echinococcus granulosus and Mesocestoides corti (Cestoda) infection in mice.

Killing of metacestodes by normal or post-infection macrophages and the regulation of this activity by cytokines were studied in vitro. The protoscolecidal activity of normal macrophages against Echinococcus granulosus was inhibited by a product of naive T-enriched lymphocytes co-cultured with protoscoleces (PSC). By contrast, supernates from co-cultures of Mesocestoides corti tetrathyridia (MCT) and T-enriched or B-enriched normal lymphocytes increased killing of MCT by normal macrophages. Larvicidal activity (against both PSC and MCT) was enhanced by high concentrations of macrophage-activating factors produced by Con A-stimulated rat lymphocytes (Con A-LK), but was reduced by low concentrations of these factors. Activation by synergism between Con A-LK and recombinant interferon-gamma(r. IFN-gamma) was demonstrated in macrophage-mediated killing of MCT at high effector to target ratio. Cytokine-activation of normal or post-MCT infection macrophages was compared. Macrophages from both 8 and 20 week post-infection mice were refractory to lymphokines from lymphocyte-MCT cultures and displayed greatly reduced killing of MCT. Macrophage activation by Con A-LK and r.IFN-gamma was also impaired, implying a general defect in the ability of these post-infection macrophages to respond to macrophage activating signals. The data indicate that two different mechanisms may exist by which metacestodes regulate potentially larvicidal effector mechanisms. E. granulosus can elicit the production of lymphokines suppressive for PSC killing, whereas M. corti appears directly to induce a refractory state in effector macrophages.

Animals↗
PubMed1993

The cholinergic, serotoninergic and peptidergic components of the nervous system of Moniezia expansa (Cestoda, Cyclophyllidea).

The central (CNS) and peripheral (PNS) nervous systems of the cyclophyllidean tapeworm, Moniezia expansa, were examined for the presence of cholinergic, serotoninergic and peptidergic elements using enzyme cytochemical and immunocytochemical techniques in conjunction with light and confocal scanning laser microscopy. Cholinesterase activity and 5-hydroxytryptamine- and regulatory peptide-immunoreactivities (IRs) were localized to the nerve fibres and cell bodies of all of the major neuronal components in the CNS of the worm, including the cerebral ganglia and connecting commissure, the 10 longitudinal nerve cords and associated transverse ring commissures. Although each of the 3 systems appeared well developed and comprised a significant portion of the nervous system, the serotoninergic constituent was the most highly developed, consisting of a vast array of nerve fibres and cell bodies distributed throughout the strobila of the worm. A close association of cholinesterase reactivity and peptide-IRs was evident throughout the CNS, indicating the possible co-localization of acetylcholine and neuropeptides. Within the PNS, cholinergic activity and serotoninergic- and peptidergic-IRs occurred in the subtegumental network of nerve fibres and somatic musculature. Although all 3 neurochemical elements were present in the acetabula, they were found in different nerve fibres; only cholinergic and peptidergic cell bodies were found. The common genital opening, vagina and ootype regions of the reproductive system displayed a rich innervation of all 3 types of neuronal populations. Within the peptidergic system, immunostaining with antisera raised to the C-terminus of the neuropeptide Y superfamily of peptides and the invertebrate peptides, neuropeptide F (M. expansa) and FMRFamide was the most prevalent. Limited positive-IR for substance P and neurokinin A were also recorded in the CNS of the worm.

Animals↗
PubMed1993

Ligula intestinalis (L.) (Cestoda: Pseudophyllidea): polarization of cyprinid leucocytes as an indicator of host- and parasite-derived chemoattractants.

Freshly isolated pronephric leucocytes from roach, Rutilus rutilus and gudgeon, Gobio gobio were exposed to extracts of plerocercoids of Ligula intestinalis from these two cyprinid fish. Addition of the extracts or an increase in incubation temperature from 10 to 20 degrees C induced polarization of neutrophils and L1 granulocytes. Cells were transformed from their typical spherical shape to elongate forms possessing a ruffled leading edge. Extracts obtained from gudgeon-Ligula stimulated polarization of both roach and gudgeon leucocytes at 10 and 20 degrees C. In contrast, extracts from roach-Ligula, whilst having little effect at 10 degrees C, suppressed temperature-induced polarization of leucocytes at 20 degrees C. Addition of serum to all the essays enhanced polarization and abolished the roach-Ligula-induced suppression. It is suggested that leucocyte chemoattractants are present in Ligula from roach and gudgeon and only parasites from the former host contain an inhibitor of polarization. In addition, host-derived factors possibly complement, may be involved in leucocyte chemoattraction.

Animals↗
PubMed1994

Proteinase activity in the plerocercoid of Proteocephalus ambloplitis (Cestoda).

Host invasion and tissue migration of several helminths have been linked to expression and release of parasite-derived proteinases. The plerocercoid of the cestode Proteocephalus ambloplitis can migrate into the visceral organs or, in the case of bass, from them into the intestinal tract of the same individual fish. It does this within a few hours, aided by secretion of a substance from its apical gland. Proteinase activity in this plerocercoid, obtained from the host liver, was defined by pH optimum, by substrate and inhibitor specificity, and by electrophoretic and chromatographic techniques. Homogenates of plerocercoid contained a metalloproteinase exhibiting a molecular weight of 30,000 determined by gelatin substrate gel electrophoresis. Peak activity of this proteolytic enzyme in gel filtration fractions when azocoll was used as substrate then corresponded to a molecular weight of 31,500. The proteinase showed collagenolytic, haemoglobinolytic and slight elastinolytic activity, and it had a pH optimum at 9.0. Enzyme activity could be inhibited by various chelating agents. The metalloproteinase identified in this study constitutes the only enzyme class present in this larval stage of P. ambloplitis. We suggest that the plerocercoid's metalloproteinase is the substance secreted from the apical organ, necessary for the previously recognized tissue migration phase. This enzyme might also have a nutritional function.

Animals↗
PubMed1986

Structure and ultrastructure of muscle systems within Grillotia erinaceus metacestodes (Cestoda: Trypanorhyncha).

Three distinct muscle types have been identified within the metacestode of Grillotia erinaceus. These consist of peripheral somatic myofibres plus two muscle systems directly involved in parasite attachment to the host, i.e. the tentacular bulb and its antagonistic retractor muscle. In common with other cestodes the somatic muscle consists of smooth-type fibres running longitudinally and obliquely to the main body axis. The retractor muscle consists of myofibres with centrally displaced nuclei. Upon contraction these latter fibres become spirally orientated causing the muscle to coil and lateral membranes to become elevated as spikes. Definitive nerve processes have not been identified within somatic or retractor muscle. Individual tentacular bulbs form the proximal terminus for a closed hydraulic system. Each bulb consists of overlapping, contrarotating myofibres which display obvious striations; the striations appear in alternate fibres to be in transverse and oblique planes. Adjacent myofibres are separated by approximately 0.5 micron, possess abundant mitochondria and have shallow t-tubules plus associated vesicles of sarcoplasmic reticulum at each Z line. Thick myofilaments are surrounded by 13, shared, thin myofilaments. Close neuronal control for the bulb muscle is suggested by the presence of obvious motor end-plates which contain both lucent and dense neurovesicles.

Animals↗