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PubMed1998

Morphological changes of larval Echinococcus multilocularis in mice treated with albendazole or mebendazole.

Using DBA/2J mice, tissue homogenates of larval Echinococcus multilocularis were injected into the mesenteric veins to generate the liver infection. Mice were treated with either albendazole or mebendazole for prolonged periods to examine the morphological changes of the metacestode. Albendazole induced disorganization of both laminated and germinal layers and suppressed the maturation of vesicles. Amorphous but loosely laminated PAS-positive material was observed inside the damaged vesicles, although new vesicles slightly developed inside or outside of the damaged ones. Active proliferation of vesicles occurred after treatment with albendazole was terminated. Hydatid cysts were more severely damaged in mice treated with mebendazole and new vesicles did not develop around the damaged ones. Also, hydatid cysts reappeared after treatment with mebendazole was terminated. These results indicate that these drugs do not eliminate larval E. multilocularis in the long-term, but mebendazole has a higher suppressive effect on multivesiculation than albendazole.

Albendazole↗
PubMed1986

Experimental infection of the baboon (Papio cynocephalus) with Echinococcus granulosus of camel, cattle, sheep and goat origin from Kenya.

In different areas of the world, strains of Echinococcus granulosus have been described which appear to vary in their infectivity, and laboratory primates have been used as indicators of their infectivity to man. This phenomenon was evaluated in Kenya for hydatid material of human, camel, cattle, sheep and goat origin. Viable eggs, produced by experimental infections in dogs with larval material from all the above intermediate hosts, were fed separately to four baboons (Papio cynocephalus) in each case. Baboons were autopsied between 373 and 501 days following infection and the liver, lungs, heart, spleen and kidneys were thoroughly inspected. Hydatid cysts were recovered from two baboons in each of the camel, sheep and goat groups, three baboons in the cattle group and none of the baboons in the human group. Fertile cysts were found in the cattle and goat groups and it is suggested that the baboon could be used as an experimental model for this parasite.

Animals↗
PubMed1976

Developing protoscoleces of Echinococcus granulosus on the outer surface of the brood capsule, detected by scanning electron microscopy.

By means of scanning electron microscopy, stalked protrusions were observed arising from the outer surface of intact brood capsules of Echinococcus granulosus. Histological studies showed these protrusions to be developing protoscoleces. However, complete development is not attained and the protoscoleces eventually die. It is suggested that external development is a result of overcrowding within the brood capsule.

Animals↗
PubMed1984

Echinococcus multilocularis: identification of proteins inducing antibody formation in metacestode infection.

An approach to the identification of parasite proteins which are immunogenic in natural infections is described, using the infection with the larval stage of Echinococcus multilocularis as a parasite model. Metacestode proteins were separated by SDS-polyacrylamide gel electrophoresis, and transferred electrophoretically to nitrocellulose sheets (Western blotting). Subsequently, immune recognition of the proteins was performed with various host sera and antigen-antibody complexes were detected enzymatically. Using homologous antisera, different patterns of immunogenic bands were revealed by sera of different host species. Cross-reactions with sera from individuals infected with unrelated helminths were analysed. Four proteins of E. multilocularis which failed to show any cross-reaction were identified.

Animals↗
PubMed1984

Echinococcus granulosus equinus: variation in the germinal layer of murine hydatids and evidence of autophagy.

The germinal layer of sterile 9-month-old murine peritoneal cysts of Echinococcus granulosus equinus shows interrelated variation in depth, tissue integrity, metabolic reserves and the number of autophagic lamellar bodies present. These features are similar in large and medium-sized cysts from the same host, whether occurring singly or within cyst masses. Deep germinal layers (greater than 16 micron) are lipid- and glycogen-rich and possess numerous autophagic vacuoles with 6 nm period lamellar stacks asymmetrically disposed peripherally; shallow layers (less than 12 micron), with indications of degeneration, have depleted metabolic reserves and fewer lamellar bodies. These bodies are formed by smooth endoplasmic reticulum encirclement of small glycogen masses followed by further sequestration, and eventually definition of glycogen particles may be lost. Autophagy of mitochondria and cytoplasmic vesicles also occurs. The presence of lysosomal enzymes within the layer suggests autolysosomal compartmentalization of excess substrate and effete material. Mucopolysaccharide bodies, containing material similar to that exocytosed to form the laminated layer matrix, occur and are formed from fusion and autophagy of Golgi-derived vesicles. These bodies may also develop peripheral 6 nm period lamellar stacks, but of limited depth. Mucopolysaccharide bodies are the dominant feature of the germinal layer of very small cyst-mass cysts in which laminated layer production is considered to be arrested. They thus represent a repository for the unreleased mucopolysaccharide material.

Animals↗
PubMed1982

Intermediary carbohydrate metabolism in protoscoleces of Echinococcus granulosus (horse and sheep strains) and E. multilocularis.

With few exceptions, the specific activities of the glycolytic enzymes and the steady-state content of glycolytic and associated intermediates in protoscoleces of the horse (E.g.H) and sheep (E.g.S) strains of Echinococcus granulosus and the closely related E. multilocularis (E.m.) are very similar. Phosphorylase, hexokinase, phosphofructokinase and pyruvate kinase catalyse non-equilibrium reactions and the patterns of activity for pyruvate kinase, phosphoenolypyruvate carboxykinase and malic enzyme are similar in the three organisms. The levels of tricarboxylic acid cycle intermediates in E.g.H., E.g.S. and E.m. are of the same order as those reported in tissues with an active cycle. Each has a complete sequence of cycle enzymes but there are substantial differences between the three parasites with regard to the activity of individual enzymes. The activities of NAD and NADP-linked isocitrate dehydrogenases are significantly lower in E.g.H. than in E.g.S. and particularly in E.m. which suggests that the tricarboxylic acid cycle may play a more important role in carbohydrate metabolism and energy production in the latter parasites. Nevertheless, the three organisms utilize fermentative pathways for alternative energy production, fix carbon dioxide via phosphoenolpyruvate carboxykinase and have a partial reversed tricarboxylic acid cycle. It is speculated that in vivo more carbon will be channelled towards oxaloacetate than pyruvate at the phosphonenolpyruvate branch point. The steady state content of ATP and the ATP/AMP ratios are low in the three organisms, suggesting a low rate of ATP utilization in each.

Adenosine Triphosphate↗
PubMed1976

Echinococcus granulosus: development in vitro from oncosphere to immature hydatid cyst.

Echinococcus granulosus cysts were cultured in vitro from the oncosphere, and cyst morphogenesis is described. Cysts grew to a mean diameter of 16 mm in 120 days, with a maximum of 20 mm. An amorphous layer was apparent around the larvae during early post-oncospheral re-organization. Organisms became vesicular at 6 days and laminations appeared in the amorphous layer at 10 days. Confluence of proliferating cells to form the syncytium of the germinal membrane was observed.

Animals↗
PubMed1978

Differences in the chemical composition and carbohydrate metabolism of Echinococcus granulosus (horse and sheep strains) and E. multilocularis.

Metabolic studies in vitro and studies on chemical composition indicate basic biochemical differences between the horse and sheep strains of Echinococcus granulosus and between these and the closely related species, E. multilocularis. The horse strain of E. granulosus has a similar level of DNA, but significantly more polysaccharides and lipids, with less RNA and protein than the sheep strain. E. multilocularis has significantly more lipids and DNA but less polysaccharides than the horse and sheep strains of E. granulosus, more RNA and protein than the horse strain but similar protein to and less RNA than the sheep strain. Incubations under air and under 95% N2-5% CO2 for 3 h show that only E. multilocularis takes up glucose, that all three forms consume different amounts of oxygen and endogenous glycogen and produce different concentrations of lactate, succinate, acetate, malate, pyruvate, propionate and ethanol as end products of carbohydrate metabolism.

Acetates↗
PubMed1985

Isolation, fractionation and partial characterization of the tegumental surface from protoscoleces of the hydatid organism, Echinococcus granulosus.

Several approaches were adopted for the disruption and removal of the tegumental surface from protoscoleces of the horse strain of the hydatid organism, Echinococcus granulosus. The effectiveness of each method and the purity of subsequent microthrix-enriched fractions obtained by differential centrifugation were evaluated by electron microscopy, by the amount of protein released and by the degree of enrichment of surface plasma membrane marker enzymes. Incubation in saponin for 10 min produced the purest microtriche preparation, but in low yield; freeze/thawing, incubation in Triton X-100 for 10 min or in saponin for 20 min produced fractions containing significant amounts of relatively pure microtriches, but mild homogenization was a poor method for surface disruption and subsequent isolation of microtriches. Phosphodiesterase, adenosine triphosphatase (total and ouabain-inhibited), leucine aminopeptidase and glutamyltransferase were active in the protoscoleces but none were enriched in any of the microthrix fractions. In contrast, alkaline phosphatase, acid phosphatase, 5' nucleotidase and maltase were enriched significantly in all of the isolated microtriche preparations, which suggests that these enzymes are predominantly surface membrane bound. The protein profiles of the microthrix-enriched fractions, following SDS-PAGE, were basically similar, although there were some qualitative and quantitative differences in the proteins released by each isolation procedure. Three major PAS-staining components were present in all the preparations and these probably originated from the glycocalyx. One of these PAS-positive components, with an approximate molecular weight of 110 kDa, may be a glycoprotein specific to the horse strain of E. granulosus.

Animals↗
PubMed1978

Ultrastructural immunocytochemical localization of two hydatid fluid antigens (antigen 5 and antigen B) in the brood capsules and protoscoleces of ovine and equine Echinococcus granulosus and E. multilocularis.

The unlabelled antibody method was used in the ultrastructural localization of two hydatid fluid antigens, antigen 5 and antigen B, in brood capsules and protoscoleces of Echinococcus granulosus and E. multilocularis. Antigen 5 was found in the parenchyma cells of the protoscolex and brood capsule wall and to a lesser extent in the walls of the flame cells and collecting ducts of the excretory system and in the surrounding interstitial material. It is suggested that, while some excretion of this antigen may occur from the protoscolex, it could also be liberated into the cystic cavity by degeneration of protoscoleces and parenchymal cells of the brood capsule wall. Antigen B was found mainly in the distal cytoplasm and perinuclear cytoplasm of the tegument anterior to the suckers. It is apparently secreted to the outside and was present in the brood capsule contents; it adheres to the anterior surface and the posterior periodic acid-Schiff (PAS)-positive glycocalyx of the protoscolex and to the inner surface of the brood capsule wall. The protoscolex tegument posterior to the suckers was negative. The parenchyma cells of the protoscolex and brood capsule wall were also positive although the intensity of the reaction product was variable.

Animals↗
PubMed1983

Echinococcus granulosus equinus: an ultrastructural study of murine tissue response to hydatid cysts.

Peritoneal hydatids of Echinococcus granulosus equinus of 9 months standing in BALB/c mice occurred as free cysts or cysts within cyst masses. Both showed wide variation in size and in host tissue response, and all had a well-developed laminated layer separating the host tissue response from the germinal layer. In the smallest cyst-mass cysts the host tissue response was present as remnants of the initial cellular attack involving eosinophils. Slightly larger cyst-mass cysts possessed a primary macrophage invasion which phagocytosed the remnants of the initial attack and also, though to little effect, the laminated layer material. In the largest cyst-mass cysts a second macrophage invasion, of monocyte origin, had commenced and transformation stages of these cells to macrophages were observed. No fibroblasts surrounded individual cyst-mass cysts but they were present around the cyst mass, encapsulating it and possibly preventing further host cell invasion. Thus, the host tissue response around individual cyst-mass cysts remained 'preserved' at an early stage such as existed at the time of encapsulation. Small free cysts showed a primary macrophage invasion and transformation stages of cells of a secondary infiltration of peritoneal origin. Peripheral to the macrophages were fibroblasts demonstrating limited fibrinogenesis, and each cyst was surrounded by a layer of mesothelial cells. Large free cysts, also delimited by a mesothelial layer, possessed peripheral connective tissue, a deep fibrous layer and a monolayer of very compressed macrophages lying adjacent to the laminated layer. It is emphasized that an understanding of the host tissue response in cysts of different sizes and from different locations is an essential pre-requisite for the design of experimental studies.

Animals↗
PubMed1986

Echinococcus granulosus: in vitro effect of monensin on the tegument of the protoscolex.

Protoscoleces of Echinococcus granulosus were incubated in a 10 microM solution of monensin and their viability and the ultrastructure of their tegument were monitored over a 36 h period. The earliest effects of the ionophore, apparent within 15 min, involved a degree of cisternal swelling of the tegumentary Golgi complexes. Swelling became more pronounced with time and cytons eventually contained numerous large electron-lucent vesicles. Residual bodies indicative of autophagy were observed in the cytons and distal cytoplasm from 1 h onwards. All movement of protoscoleces ceased after 1 h and the surface of the soma subsequently became folded, possibly suggesting spastic paralysis. Later, vacuoles and large cytoplasmic blebs were observed in the distal cytoplasm and viability dropped rapidly after 12 h. All protoscoleces were dead at 36 h. The potential of monensin as an in vivo protoscolicidal agent is discussed.

Animals↗
PubMed1986

Population dynamics in echinococcosis and cysticercosis: comparison of the response of Echinococcus granulosus, Taenia hydatigena and T. ovis to control.

A comparative study has been made of the progress in the control of ovine echinococcosis caused by Echinococcus granulosus and the ovine cysticercoses caused by Taenia hydatigena and T. ovis in New Zealand. The methods of control included an educational and a dog-dosing programme. In the Styx field trial, the Otago/Southland Surveillance Programme and the national control programme, E. granulosus declined towards extinction. In contrast, this same control effort transformed the cysticercoses from hyper-endemic to endemic status with focal epidemics. In this unstable state, the density-dependent constraint was negligible and superinfection occurred.

Animals↗
PubMed1975

In vitro suppression of segmentation in Echinococcus multilocularis with morphological transformation of protoscoleces into monozoic adults.

When protoscoleces of Echinococcus multilocularis were cultured in vitro, under axenic conditions in either monophasic or diphasic media, segmentation was suppressed in most organisms, some 70-80% of which developed into unsegmented, monozoic forms with a complete set of sexually mature male and female genitalia. The most striking feature of monozoic worms was the large lateral swelling produced by the cirrus sac the effect being to produce organisms with an unusual asymmetric shape. Worms which did not become monozoic either (a) underwent some somatic growth, developed two sets of genitalia and became 'pseudo-segmented', i.e. with the inter-proglottid membranes absent or poorly defined, or (b) became vesicular or abnormal. The mechanisms which could be involved in the suppression of somatic growth and the induction of the monozoic condition, are examined in terms of cell lineage. The possible significance of these results in understanding the evolution of the cestodes is discussed.

Animals↗
PubMed1987

Population dynamics in echinococcosis and cysticercosis: evaluation of the biological parameters of Taenia hydatigena and T. ovis and comparison with those of Echinococcus granulosus.

An evaluation has been made of the biological and epidemiological parameters that determine the basic reproductive rates of Taenia hydatigena and T. ovis. These host-parasite systems are characterized by (i) no overcrowding in either host; (ii) no parasite-induced mortality of either host; (iii) no density-dependent constraint in the definitive host, but a strong, rapidly mobilized, short-acting immunity in the intermediate host and (iv) egg production which, in the natural environment, is high enough to prevent superinfection. It is considered that tapeworms with these characteristics are more stable to fluctuations in environmental conditions and to control measures such as dog dosing, than species which have a low egg production and infectivity such as Echinococcus granulosus. Reciprocal immunity exists between T. hydatigena and T. ovis in sheep. Exposure to T. hydatigena suppresses infection by T. ovis, but not by E. granulosus. This has important epidemiological consequences where these parasites co-exist.

Animals↗
PubMed1987

Echinococcus granulosus: changes in the surface ultrastructure during protoscolex formation.

Changes in the tegumentary projections of protoscoleces of Echinococcus granulosus, developing within brood capsules, were examined at the ultrastructural level. The original scant covering of spineless, truncated microtriches was supplemented by a population of microvilli covering the entire surface of protoscoleces in the early stages of formation. As differentiation continued, rostellar hooks were formed by enlargement of single large (T1) microtriches, and normal spined microtriches were produced on the sucker region. These were formed in two ways: by addition of spine material to the truncated microtriches, and de novo followed by up-lifting from the tegumentary surface. A second type of large microthrix (T2) was present in a band immediately below the developing hooks. These microtriches appeared to be formed from a fusion of existing microtriches, but were subsequently lost prior to scolex invagination. The microvilli were also shed from both the sucker and soma regions, to be replaced by microtriches and small blunt elevations respectively.

Animals↗
PubMed1987

Experimental Echinococcus granulosus infection in mice: immunocytochemical analysis of lymphocyte populations in local lymphoid infections during early infection.

The influence of subcutaneous infection with protoscoleces of Echinococcus granulosus on the distribution of lymphocyte subsets in draining lymph nodes has been evaluated by immunocytochemical labelling of lymphocyte surface antigens. These studies reveal marked expansion of paracortical Thy-1+, Lyt-1+ cells and moderate proliferation of surface immunoglobulin-bearing B-cells immediately after infection. The Lyt-1+:Lyt-2+ ratio decreases rapidly during the first 21 days post-infection and remains below unity until at least 12 weeks post-infection due to severe depletion of Lyt-1+ cells in draining lymph nodes and a significant increase in the percentage of Lyt-2+ cells. The potential role of these Lyt-1-,2+ (putative T-suppressor) cells in regulation of the anti-parasite immune response and mediation of generalized immunosuppression is discussed in the light of evidence of inhibition of anti-parasite immunity in infected mice.

Animals↗
PubMed1987

Echinococcus granulosus: specificity of amino acid transport systems in protoscoleces.

Protoscoleces of Echinococcus granulosus absorb the L-amino acids proline, methionine, leucine, alanine, serine, phenylalanine, lysine and glutamic acid by a combination of mediated transport and diffusion. All eight amino acids were accumulated against a concentration gradient. Comparison of Kt and Vmax values suggests that a low affinity for a particular compound is compensated for by a relatively larger number of transport sites for that compound. Four systems serve for the transport of the eight substrates studied: 2 for neutral (EgN1, EgN2) and 1 each for acidic (EgA) and basic (EgB) amino acids. All eight amino acids are incorporated into protein to varying degrees and substantial portions of absorbed L-alanine and L-methionine are metabolized into other compounds.

Absorption↗