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PubMed1981

A study of the initiation of biliary hyperplasia in rats infected with Fasciola hepatica.

Following infection of rats with Fasciola hepatica, an increase in the number of epithelial cells in the common bile duct, labelled with [3H]thymidine, was detected autoradiographically as early as 5 days post-infection (p.i.). This initial mitogenic effect of the infection was limited to that region of the bile duct lying adjacent to the liver, while the region lying next to the duodenum failed to show any increase in labelling until 41 days p.i. Mechanical contact between the parasite and the biliary epithelium did not occur until 41 days p.i. and the initial hyperplasia was evidently not a result of mechanical irritation. The study serves to emphasize the chemical aetiology of the precocious biliary hyperplasia and to more accurately identify its onset.

Animals↗
PubMed1981

Purification and characterization of phosphoglycerate kinase from Fasciola hepatica.

Phosphoglycerate kinase (EC 2.7.2.3) of Fasciola hepatica was purified 375-fold to homogeneity. The enzyme was monomeric, and had a molecular weight of 47 900 and a sedimentation coefficient of 3.0-3.5 S. The enzyme was composed of 397 amino acids and was relatively rich in sulfur amino acids containing 13 methionine and 2 cysteine residues per mole. The enzyme possessed a highly reactive essential sulfhydryl group and was inhibited irreversibly by iodoacetamide and N-ethylmaleimide and reversibly by p-chloromercuribenzoate and 5,5'-dithio-bis(2-nitrobenzoic acid). Initial velocity studies suggested that reaction occurred via a sequential mechanism. The Km values for 3-phosphoglycerate and ATP were 1.26 and 0.90 mM, respectively. ADP was a noncompetitive inhibitor with respect to both ATP and 3-phosphoglycerate.

Amino Acids↗
PubMed1976

Molluscs interfering with the capacity of Fasciola hepatica miracidia to infect Lymnaea truncatula.

Fasciola hepatica miracidia labelled with radioselenium were used to study aspects of their host-finding capacity by determining radioactivity subsequently taken up by exposed 'target' snails (Lymnaea truncatula). Possible interfering effects exercised by a number of non-host snails and bivalves were examined in linear test channels. The infection rate (radioactivity) among 'target' snails was markedly lowered when non-host Lymnaea species (L. pereger, L. palustris, L. stagnalis) were interposed as 'decoys'. The prosobranch Bithynia tentaculata and the bivalve Sphaerium corneum exhibited a slight decoy effect whereas pulmonate species like Anisus vortex, Gyraulus albus, Planorbis planorbis, Physa fontinalis did not interfere with miracidial host-finding. Other experiments showed that miracidia are more strongly attracted towards L. truncatula than L. pereger. Miracidia are not able to penetrate intact egg clusters of L. truncatula.

Animals↗
PubMed1982

Characterization of excretory-secretory antigens of Fasciola hepatica.

Twenty-one day old Fasciola hepatica were recovered from the livers of infected mice and cultured for 5-7 days in a serum-free medium containing either [14C]leucine, [14C]isoleucine or [35S]methionine, or in a medium containing [14C]leucine and serum from sheep vaccinated with excretory-- secretory (ES) antigens of juvenile F. hepatica. All three labelled amino acids were incorporated into fluke proteins. Labelled proteins also appeared in the culture medium. Three major polypeptides detected in the culture media had apparent molecular weights of 26,000, 24,000 and 23,000. All were immunoprecipitated from [14C]leucine-labelled culture medium using antisera against fluke somatic antigens raised in rabbits or from sheep vaccinated with ES antigens of juvenile F. hepatica. A polypeptide of molecular weight 27,000 was also prominent in the culture medium when [14C]isoleucine was used. This polypeptide was present was a minor component when [14C]leucine and [35S]methionine were included in the culture media; it did not appear to be immunoprecipitated by the above antisera from [14C]leucine-labelled culture medium. In the presence of serum from vaccinated sheep, the ES antigens formed immune complexes which contained the polypeptides mentioned above, together with several higher molecular weight polypeptides. Additionally, a number of minor bands of varying molecular weight were present. After micro-Ouchterlony gel immunodiffusion, 2 precipitin lines formed between the labelled ES antigens and antisera. Electrophoresis of these indicated that the 23,000, 24,000 and 26,000 Dalton labelled polypeptides were present in each. The higher molecular weight and the 27,000 Dalton labelled polypeptides were also present in one of the lines.

Animals↗
PubMed1986

Early migration of radiolabeled larvae of Fasciola hepatica in the mouse.

Metacercariae of Fasciola hepatica were labeled with 75Se by exposure of infected Lymnaea columella to 75Se-M, 20 muCi/snail, in 5 ml of water. Seventy-two mice were inoculated with 50 75Se-labeled metacercariae. At intervals after infection, the distribution of metacercariae in gut, body cavities and liver was studied by compressed organ autoradiography, and a variant of this technique adapted to gut content and body cavity washes. Ag degree focus counts from autoradiograms expressed as percentage of actual exposure level were subjected to probit analysis. Estimates of the average departure time of radio-labeled maritas from gastrointestinal tracts and average arrival time into the abdominal cavities were 12.2 and 12.5 h, respectively. The peak accumulation of maritas in abdominal cavities occurred at 24 h post-inoculation. A 7.7-h discrepancy between estimated average departure time from abdominal cavities (92 h) and average arrival time at livers (99.7 h) was attributed to experimental error.

Animals↗
PubMed1981

Scanning electron microscopy of in vitro serum-mediated destruction of juvenile Fasciola hepatica.

The tegumental surface of immature Fasciola hepatica was damaged when incubated in vitro with serum collected from an experimentally infected calf. Degeneration of the tegumental surface was observed by scanning electron microscopy (SEM) at 4 hr. after incubation. Decomposition was observed 8 to 12 hr after incubation and complete destruction of the tegument occurred by 16 hr. The flukes became inactive after 8 to 12 hr of incubation. None of the above findings were observed for the tegument of flukes incubated in tissue culture media or in media containing normal calf serum and the trematodes remained motile throughout the incubation period. Latex particles were used as an immunological marker for SEM studies to determine if gamma globulin could be responsible for the observed changes and, if so, the site of antibody attachment. The coated latex particles covered the entire surface of flukes recovered from mice 5 days after infection with metacercariae. In contrast, latex particles coated with either normal gamma globulin or gamma globulin from serum of the experimentally infected calf that had been adsorbed with disrupted adult flukes were not attached to the surface of the flukes. Absorption of the serum with disrupted, adult flukes decreased the concentrations of immunoglobulins (Ig)G1 and G2 whereas IgA and IgM were apparently not affected.

Animals↗
PubMed2004

Fasciola hepatica infestation as a very rare cause of extrahepatic cholestasis.

Fasciola hepatica, an endemic parasite in Turkey, is still a very rare cause of cholestasis worldwide. Through ingestion of contaminated water plants like watercress, humans can become the definitive host of this parasite. Cholestatic symptoms may be sudden but in some cases they may be preceded by a long period of fever, eosinophilia and vague gastrointestinal symptoms. We report a woman with cholangitis symptoms of sudden onset which was proved to be due to Fasciola hepatica infestation by an endoscopic retrograde cholangiography.

Adult↗
PubMedDate not supplied

[Identification of the catecholamines in tissue extracts of the trematode, Fasciola hepatica].

Dopamine was identified in extracts from Fasciola hepatica by the fluorometric method. It was found that the dopamine concentration in F. hepatica was 0.668 +/- 0.027 micrograms/g of wet weight. The head region (including the oral and ventral suckers) contained 1.658 +/- 0.275 micrograms/g of dopamine (0.016 +/- 0.002 micrograms per parasite), while the posterior region (located behind the ventral sucker) contained 0.278 +/- 0.070 micrograms/g of dopamine (0.014 +/- 0.004 micrograms per parasite). When the worms were treated with DL-DOPA, the concentration of dopamine increased. In helminths treated with reserpine a marked decline of dopamine level was observed. Adrenaline and noradrenaline were not detectable in F. hepatica.

Animals↗
PubMed2005

Infection with Fasciola hepatica.

Fascioliasis, caused by the liver fluke Fasciola hepatica, is an infection that occurs worldwide, although humans are accidental hosts. F. hepatica infection comprises two stages, hepatic and biliary, with different signs and symptoms. Stool examination and ELISA can be used for the initial diagnosis. Radiographic techniques, such as computerised tomography and ultrasonography, as well as magnetic resonance imaging, are used widely for confirmation and follow-up of the disease. Invasive techniques, such as percutaneous cholangiography, endoscopic retrograde cholangiography and liver biopsy, may aid in the diagnosis but are not essential. Triclabendazole is recommended as the first-line agent for the treatment of F. hepatica infection, with bithionol as an alternative.

Animals↗
PubMed1984

A review of the antigens of Fasciola hepatica.

The interaction between the antigens of Fasciola hepatica and the host immune response are reviewed. This paper evaluates not only more recent work, but the older literature as well. Antigens from each stage in the life cycle are considered with the idea of identifying those antigens with a potential for use in an effective vaccine. Antigens which cross-react with other parasite species are detailed as well as those that cross-react between different stages in the life cycle of F. hepatica. The objective of the review is to demonstrate for other investigators that vaccination against F. hepatica is a distinct possibility. We hope to encourage more investigators to initiate work on this aspect of an economically-important cosmopolitan parasite.

Animals↗
PubMed1978

Activation of succinate dehydrogenase from adult Fasciola hepatica (Trematoda).

The succinate dehydrogenase of adult Fasciola hepatica was found to exist in active and in active forms. The enzyme was inactivated by 1 micron oxaloacetate and activated by incubation with compounds which bind to the active site (succinate, fumarate, malonate) or by incubation with anions and certain nucleotides. The activation of the enzyme by succinate followed first-order kinetics. The extent of activation of F. hepatica succinate dehydrogenase depended on the nature and concentration of the activator and on the pH. The rate of activation of the enzyme depended on the temperature. In contrast, the fumarate reductase activity of F. hepatica was not activated by incubation with substrate or anions and was not inhibited by oxaloacetate (100 micron). The significance of these results in the regulation of the tricarboxylic acid cycle in parasitic helminths is discussed.

Animals↗
PubMed2001

Identification of fatty acid molecules in a Fasciola hepatica immunoprophylactic fatty acid-binding protein.

Fasciola hepatica adult flukes have a native protein complex denoted nFh12 and consisting of fatty acid binding proteins that comprise at least 8 isoforms. It is a potent immunogen because in several animal hosts it induces an early antibody response to F. hepatica infection. It is also a potent cross-protective immunogen because it induces a protective immune response in mice to challenge infection with Schistosoma mansoni cercariae. The gene encoding this protein has been cloned and sequenced. It produces a polypeptide of 132 amino acids with a predicted molecular mass of 14.7 kDa and is denoted rFh15. It also has a significant homology to a 14-kDa S. mansoni fatty acid binding protein (Sm14). In the present study, nFh12 was delipidated with charcoal treatment and then studied by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Additionally, a lipid analysis of nFh12 was undertaken using gas chromatography-mass spectrometry to demonstrate that the nFh12 protein complex is, in fact, a complex of fatty acid binding proteins. Five long-chain saturated and unsaturated fatty acids were detected. The most abundant were palmitic acid (38%), stearic acid (24%), and oleic acid (13%). These fatty acid molecules do not have covalent bonds attached to the protein molecule. Because both nFh12 and Sm14 protect mice against challenge infection with F. hepatica and S. mansoni, it is possible that they have common protective epitopes in which fatty acids could be involved. Further studies are in progress to determine the chemical nature of these potential common epitopes.

Animals↗
PubMed1977

[Experimental infection of horses with Fasciola hepatica].

Ten pony foals were infected with Fasciola hepatica; five animals received up to 1000 metacercariae orally, the remaining animals received up to 80 specimens of 24 hours old adulescariae intraperitoneally. The rate of development of the parasites varied in a wide range between 0,2 and 41%. Most of the liverflukes were found in animals severely infected with strongyles in the same time. Only 22 weeks after oral infection, the flukes had reached a length of 20 mm and sexual maturity. Fasciola-eggs could not be detected in the feces.

Animals↗
PubMed1992

Humoral and cellular immune responses in rats during a primary infestation with Fasciola hepatica.

The antibody and lymphocyte responses to Fasciola hepatica were studied in rats. Infested rats were shown to produce antibodies against excretory-secretory (ES) products of adult flukes as early as the first week after infestation. Immunoblotting revealed fractions of ES products of adult flukes to which antibodies were progressively produced during the course of the infestation. Proliferation of peripheral blood lymphocytes, splenocytes and thymocytes when incubated with different mitogens (Concanavalin A (ConA) or Pokeweed mitogen (PWM) or different liver fluke antigens (metacercariae antigen (EM) or ES products of adult flukes) have been studied. In response to these mitogens or antigens, splenocytes were stimulated on the second and fourth weeks after infestation. Thymocytes were significantly activated by PWM on the second week but peripheral blood lymphocytes did not show any statistically significant response. Results obtained in antibody production, immunoblotting and lymphocyte proliferation suggested sequential releases of F. hepatica substances and the existence of common proteins between adult and juvenile parasite stages. Cellular and humoral responses observed in this work did not seem to confer a complete resistance to liver fluke primary infestation on the rat.

Animals↗
PubMed1992

Primary sequence heterogeneity and tissue expression of glutathione S-transferases of Fasciola hepatica.

Glutathione S-transferases (GSTs) from Fasciola hepatica have been purified by glutathione affinity chromatography. Two closely migrating species of Mr 26,000 and 26,500 were identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and several species resolved by two-dimensional gel analysis, indicating substantial heterogeneity among the GSTs. N-terminal amino acid sequencing revealed one core sequence containing three polymorphisms, whereas the sequence of GST peptides implied a minimum of three different GSTs. The amino acid sequence data assigned the F. hepatica GSTs to the mu class of GSTs with high similarities to these proteins in other helminths and mammals. The native GSTs of F. hepatica appeared to behave as dimers as determined by molecular sieving chromatography. The observation that the GSTs of F. hepatica are heterogeneous in sequence and behave as dimers in the native state suggest that these isoenzymes may exhibit considerable functional heterogeneity which may be of importance to the parasite. Immunocytochemical studies suggest that the main source of GST in F. hepatica are the parenchymal cells and peripheral tissues of the parasite. Some extracellular GST is associated with the lamellae of the intestinal epithelium. The identification of an intestinal GST is unique among trematodes studied to date.

Amino Acid Sequence↗
PubMed2001

Heterologous expression and functional characterization of thioredoxin from Fasciola hepatica.

The full thioredoxin coding sequence from Fasciola hepatica has been cloned into the pGEX-2T expression vector and produced in Escherichia coli as a fusion protein. The recombinant protein proved to be biologically active, using an insulin reduction assay, and was also able to activate thioredoxin peroxidase from F. hepatica. These observations suggest that this protein could participate in a redox cascade involved in the maintenance of cell homeostasis as well as in parasite protection against reactive oxygen species produced by the host.

Amino Acid Sequence↗