Localisation of actin in the liver fluke, Fasciola hepatica

Protein and antigen profiles of third-stage larvae of Gnathostoma spinigerum assessed with next-generation sequencing transcriptomic information

Gnathostomiasis is a food-borne zoonotic disease that can affect humans who eat improperly cooked meat containg infective third-stage larvae. Definitive diagnosis is through larval recovery. However, this is an invasive technique and is impractical if the larvae have encysted in inaccessible areas of the body. Antigen or antibody detection might be more interesting techniques for diagnosis. Proteomic could elucidate diagnostic markers and improve our understanding of parasite biology. However, proteomic studies on Gnathostoma spinigerum are hampered by the lack of a comprehensive database for protein identification. This study aimed to explore the protein and antigen profiles of advanced third-stage G. spinigerum larvae (aL3Gs) using interrogation of mass spectrometry data and an in-house transcriptomic database for protein identification. Immunoproteomic analysis found 74 proteins in 24-kDa SDS-PAGE bands, which is size-specific for the immunodiagnosis of gnathostomiasis. Moreover, 13 proteins were found in 2-DE 24-kDa bands. The data suggest that collagenase 3, cathepsin B, glutathione S-transferase 1, cuticle collagen 14, major antigen, zinc metalloproteinase nas-4, major egg antigen, peroxiredoxin, and superoxide dismutase [Cu–Zn] may be good candidates for novel human gnathostomiasis diagnostic assays. These findings improve our understanding of the parasite’s biology and provide additional potential targets for novel therapeutics, diagnostics, and vaccines.

Profiling the glycome of Cardicola forsteri, a blood fluke parasitic to bluefin tuna

Infections by blood flukes (Cardicola spp.) are considered the most significant health issue for ranched bluefin tuna, a major aquaculture industry in Japan and Australia. The host-parasite interfaces of trematodes, namely their teguments, are particularly rich in carbohydrates, which function both in evasion and modulation of the host immune system, while some are primary antigenic targets. In this study, histochemistry and mass spectrometry techniques were used to profile the glycans of Cardicola forsteri. Fluorescent lectin staining of adult flukes indicates the presence of oligomannose (Concanavalin A-reactive) and fucosylated (Pisum sativum agglutinin-reactive) N-glycans. Additionally, reactivity of succinylated wheat germ agglutinin (s-WGA) was localised to several internal organs of the digestive and monoecious reproductive systems. Glycan structures were further investigated with tandem mass spectrometry, which revealed structures indicated by lectin reactivity. While O-glycans from these adult specimens were not detectable by mass spectrometry, several oligomannose, paucimannosidic, and complex-type N-glycans were identified, including some carrying hexuronic acid and many carrying core xylose. This is, to our knowledge, the first glycomic characterisation of a marine platyhelminth, with broader implications for research into other trematodes.

Transcriptome and Secretome Analysis of Intra-Mammalian Life-Stages of Calicophoron daubneyi Reveals Adaptation to a Unique Host Environment

Paramphistomosis, caused by the rumen fluke, Calicophoron daubneyi, is a parasitic infection of ruminant livestock, which has seen a rapid rise in prevalence throughout Western Europe in recent years. After ingestion of metacercariae (parasite cysts) by the mammalian host, newly excysted juveniles (NEJs) emerge and invade the duodenal submucosa, which causes significant pathology in heavy infections. The immature flukes then migrate upward, along the gastrointestinal tract, and enter the rumen where they mature and begin to produce eggs. Despite their emergence, and sporadic outbreaks of acute disease, we know little about the molecular mechanisms used by C. daubneyi to establish infection, acquire nutrients, and avoid the host immune response. Here, transcriptome analysis of four intramammalian life-cycle stages, integrated with secretome analysis of the NEJ and adult parasites (responsible for acute and chronic diseases, respectively), revealed how the expression and secretion of selected families of virulence factors and immunomodulators are regulated in accordance with fluke development and migration. Our data show that while a family of cathepsins B with varying S2 subsite residues (indicating distinct substrate specificities) is differentially secreted by NEJs and adult flukes, cathepsins L and F are secreted in low abundance by NEJs only. We found that C. daubneyi has an expanded family of aspartic peptidases, which is upregulated in adult worms, although they are under-represented in the secretome. The most abundant proteins in adult fluke secretions were helminth defense molecules that likely establish an immune environment permissive to fluke survival and/or neutralize pathogen-associated molecular patterns such as bacterial lipopolysaccharide in the microbiome-rich rumen. The distinct collection of molecules secreted by C. daubneyi allowed the development of the first coproantigen-based ELISA for paramphistomosis which, importantly, did not recognize antigens from other helminths commonly found as coinfections with rumen fluke.

Are glial cells of the Digenea (Platyhelminthes) muscle cells?

Muscle cells of a digenean fish blood fluke, Aporocotyle simplex, aggregate along the periphery of the cerebral ganglia. Solitary myocytons and sarcoplasmic processes with muscle fibres give rise to long, narrow lamellate projections, which are visible along the periphery and within ganglia. These ultrastructural observations suggest a switching of glial functions to muscle cells and represent additional evidence of the phylogenetic lability of glial cells in bilaterians.

Unique ultrastructural characteristics of the tegument of the digenean blood fluke Aporocotyle simplex Odhner, 1900 (Digenea: Aporocotylidae), a parasite of flatfishes

This paper includes the first transmission electron microscopical (TEM) study of the tegument of a member of the basal digenean family Aporocotylidae. Scanning electron microscopical investigations of the fish blood fluke Aporocotyle simplex show that each boss on the lateral body surface bears 12-15 simple, uniform spines which extend from 0.5-2.7 μm above the surface of the boss. TEM observations revealed that these spines reach deep beneath the distal cytoplasm of the tegument for much of their length (9-12 μm) and are surrounded by a complex of diagonal muscles in each boss. This is the first record of any digenean with so-called 'sunken' spines. The results suggest that aporocotylid spines arise from within the sarcoplasm of the boss diagonal muscles. The sunken cell bodies (perikarya) of the tegument are connected to the distal cytoplasm via ducts (specialised processes lined by microtubules); this in contrast to other digeneans studied, where they are connected via non-specialised cytoplasmic processes. Within the distal cytoplasm, the tegumental ducts of A. simplex are surrounded by invaginations of the basal membrane and release their cytoplasmic inclusions into the distal cytoplasm. These apparently unique morphological features of the tegument, especially the deep origin of the spines, may represent useful characteristics for understanding aporocotylid relationships, especially in view of the known variation in the spine patterns of aporocotylids.

Pharmacological and morphological characteristics of the muscular system of the giant liver fluke (Fascioloides magna - Bassi 1875)

Motility is required for feeding, reproduction and maintenance of the fluke in the host's liver. According to that, the neuromuscular system can be an attractive drugable target for chemotherapy. Musculature of the Fascioloides magna is organized into three layers, an outer circular layer, beneath this layer the longitudinal layer, and third, the oblique, or diagonal layer underlies the longitudinal layer. In our study, the administration of atropine or caffeine did not cause classic muscle contractions of F. magna muscle strips. However, the Electrical Field Stimulation (EFS) induced stable and repeatable contractions, which enabled us to examine their sensitivity to the various substances. Acetylcholine (ACh) (300 μM and 1 mM), caused only a slight relaxation, without affecting the amplitude of spontaneous contractions or the amplitude of contractions induced by EFS. Contrary to that, atropine (100 μM) caused a significant increase in the basal tone and an increase of EFS-induced contractions. If acetylcholine is an inhibitory neurotransmitter in trematodes, the described effects of atropine are achieved by the blockade of inhibitory neurotransmission. On the other hand, with respect to the process of excitation-contraction coupling, the plant alkaloid ryanodine (30 μM) significantly reduced the basal tone, as well as EFS-induced contractions of F. magna muscle strips. Ryanodine inhibited the potentiating effect of atropine on the basal tone and contractions caused by EFS, which indicates that the contractile effect of atropine is dependent on Ca(++) release from intracellular stores. Caffeine (500 μM) caused relaxation of fluke muscle strips and at the same time significantly enhanced the EFS-induced contractions. Both effects of caffeine can be explained by entry of extracellular Ca(++) into muscle cells. The muscle contractility of F. magna depends both on the entry of extracellular calcium, and calcium release from intracellular stores, which are under the control of RyRs. Our results also suggest that antitrematodal drugs could potentially be developed from substances with selective anti-cholinergic activity.

A novel calmodulin-like protein from the liver fluke, Fasciola hepatica

An 18.2 kDa protein from the liver fluke, Fasciola hepatica has been identified and characterised. The protein shows strongest sequence similarity to egg antigen proteins from Schistosoma mansoni, Schistosoma japonicum and Clonorchis sinensis. The protein is predicted to adopt a calmodulin-like fold; it thus represents the third calmodulin-like protein to be characterised in F. hepatica and has been named FhCaM3. Compared to the classical calmodulin structure there are some variations. Most noticeably, the central, linker helix is disrupted by a cysteine residue. Alkaline native gel electrophoresis showed that FhCaM3 binds calcium ions. This binding event increases the ability of the protein to bind the hydrophobic fluorescent probe 8-anilinonaphthalene-1-sulphonate, consistent with an increase in surface hydrophobicity as seen in other calmodulins. FhCaM3 binds to the calmodulin antagonists trifluoperazine and W7, but not to the myosin regulatory light chain binding compound praziquantel. Immunolocalisation demonstrated that the protein is found in eggs and vitelline cells. Given the critical role of calcium ions in egg formation and hatching this suggests that FhCaM3 may play a role in calcium signalling in these processes. Consequently the antagonism of FhCaM3 may, potentially, offer a method for inhibiting egg production and thus reducing the spread of infection.

Biochemical characterization and differential expression of a 16.5-kilodalton tegument-associated antigen from the liver fluke Fasciola hepatica

A cDNA encoding a 16.5-kDa protein termed FhTP16.5 was identified by immunoscreening of a cDNA library from Fasciola hepatica adult flukes using pooled sera from rabbits infected with F. hepatica for 4 weeks. Quantitative reverse transcriptase PCR (qPCR) analysis revealed that FhTP16.5 is not expressed in unembryonated eggs. It is poorly expressed in miracidia and highly expressed at the juvenile and adult stages; however, significant differences were found between the expression levels of FhTP16.5 in juveniles versus adult flukes. Recombinant FhTP16.5 was expressed at high levels in Escherichia coli, purified by affinity chromatography, and used to raise anti-FhTP16.5 polyclonal antibodies in rabbits. Immunoblot analysis using the anti-FhTP16.5 IgG antibody identified FhTP16.5 in crude and tegumental extracts and in excretory-secretory products of F. hepatica. The protein was not detected in crude extracts of Schistosoma mansoni or Schistosoma japonicum. Antibodies to FhTP16.5 were detected in the sera of rabbits at 3 to 12 weeks of F. hepatica infection as well as in the sera of humans with chronic fascioliasis; these findings suggest that FhTP16.5 could be a good antigen for serodiagnosis of fascioliasis. Immunohistochemistry demonstrated that FhTP16.5 localizes to the surface of the tegument of various developmental stages and in parenchymal tissues of the adult fluke. Such specific localization makes FhTP16.5 an attractive target for immunoprophylaxis or chemotherapy.

Myogenesis in two polyclad platyhelminths with indirect development, Pseudoceros canadensis and Stylostomum sanjuania

Myogenesis of two representatives of Platyhelminthes, Stylostomum sanjuania and Pseudoceros canadensis, was followed from egg deposition until well-differentiated free-swimming larval stages, using F-actin staining and confocal laserscanning microscopy. Zonulae adhaerentes are the only structures to stain before 50% of development between egg deposition and hatching in S. sanjuania, and before 67% of development in P. canadenis. Subsequently, irregular fibers appear in the embryo, followed by a helicoid muscle close to the apical pole. Three longitudinal muscle pairs form, of which the dorsal pair remains more pronounced than the others. Gradually, new muscles form by branching or from double-stranded muscle zones adjacent to existing muscles. This results in an elaborate muscular bodywall that consists of a single helicoid muscle as well as multiple circular and longitudinal muscles. Diverse retractor muscles insert at the sphincter muscles around the stomodeum. The overall arrangement and formation mode of the larval musculature appears very similar in both species, although only P. canadensis has a primary circular muscle posterior to the helicoid muscle. Muscle formation in the apical region of the embryo precedes that at the abapical pole and the primary longitudinal muscles form slightly later than the primary circular muscles. Myogenesis and larval myoanatomy appears highly conserved among polyclad flatworms, but differs significantly from that of other trochozoan clades. Our data suggest that the larval muscular ground pattern of polyclad larvae comprises a bodywall consisting of a helicoid muscle, circular and longitudinal muscles, several retractor muscles, and sphincter muscles around the stomodeum.

Proteomic analysis of in vitro newly excysted juveniles from Fasciola hepatica

Fasciolosis is a world-wide distributed zoonotic disease affecting several herbivores, and represents an important factor of economic loss in animal meat producing industries. In addition, specific risk factors and geographic areas for Fasciola hepatica human infection have been heavily reported recently. Several aspects related with this disease, e.g., drug resistance and prevention through vaccination, have yet to be solved. After ingestion, the infective stage for the vertebrate host-metacercariae - hatch in duodenum and the newly excysted juveniles (NEJ) penetrate the intestinal wall. The identification of proteins expressed by NEJ and specifically those found in the host-parasite interface could help understanding the first steps of animal and human infection by F. hepatica. Here we use a proteomic approach to identify a set of proteins enriched at the host-parasite interface from in vitro NEJ by applying liquid chromatography and tandem mass spectrometry (LC-MS/MS) analysis. Using this approach, we identified numerous proteins related with several biological processes of the parasite. In addition, we characterize one of the identified molecules, the 14-3-3z protein, and demonstrate its association with the outer structures of NEJ and its presence in both somatic and secretory components from the parasite. The NEJ proteins described here, together with those previously described by others, could provide new insights into the biology of the parasite and its relationship with the vertebrate host at the beginning of the infection.

Ultrastructural changes induced in the tegument and gut of Fasciola hepatica following in vivo and in vitro drug treatment with nitroxynil (Trodax)

Male Sprague-Dawley rats were dosed orally with nitroxynil at a concentration of 40 mg/kg, and adult Fasciola hepatica were recovered after 24, 48 and 72 h. Fine structural changes to the tegument and gut were monitored by transmission electron microscopy. Flukes were also incubated for 24 h in vitro in nitroxynil at a concentration of 100 microg/ml. Following treatment in vivo, there was an accumulation and accelerated release of secretory bodies at the apex of the tegumental syncytium. Some swelling of the mucopolysaccharide masses surrounding the basal infolds was evident after 48 and 72 h. There was an initial accumulation of T1 secretory bodies at the base of the syncytium, but this decreased at 72 h, coinciding with a decline in their production in the tegumental cells. The mitochondria were consistently swollen in the tegumental cells. At 72 h, large vacuolations were observed between the muscle layers and there was flooding around the underlying tissues. Some tegumental cells were seen to be degenerating and beginning to disintegrate. After 24 h treatment in vitro, the basal infolds were swollen and the crystalline structure of the spines was disrupted. Flooding of the internal tissues was evident and, in the tegumental cells, Golgi complexes and secretory bodies were absent. The mitochondria in the tegumental cells were swollen. In the gastrodermal cells, changes were evident at the earliest time period in vivo. The lamellae were disrupted, few secretory bodies were present, the mitochondria and cisternae of granular endoplasmic reticulum (ger) were swollen and there was an increased number of secretory bodies. These changes became progressively more severe with time. Similar changes were evident following treatment in vitro; vesiculation of the ger was also seen. The results indicate that oral uptake is the predominant route of entry of nitroxynil into the fluke.

Immunolocalization of cytoskeletal components in the tegument of the 3-week-old juvenile and adult Fasciola gigantica

Components of three cytoskeletal elements, namely, microtubule, intermediate and actin filaments have been localised in the tegument of the 3-week-old juvenile and adult Fasciola gigantica by means of immunofluorescence and immunoperoxidase techniques, using mouse monoclonal anti-alpha-tubulin, anti-cytokeratin antibodies and biotinylated-phalloidin, respectively. The immunostaining with the above probes were also performed in adult Schistosoma mansoni for comparison. The presence of tubulin, indicative of microtubules, was demonstrated in the tegumental cell bodies, their cytoplasmic processes, and the basal layer of the tegumental syncytium of F. gigantica. While in S. mansoni, tubulin appeared as vertical lines stretching across the whole thickness of the syncytium. Cytokeratin, representing one type of intermediate filaments, was detected in the tegumental cell bodies, their cytoplasmic processes, tegumental syncytium and spines of F. gigantica. In contrast, cytokeratin was evident only in the syncytium of S. mansoni, but not in the spines. Phalloidin, which could bind to actin, a subunit of microfilament, was detected in the tegumental cell bodies, their processes, and the microtrabecular network which form the scaffold of the tegumental syncytium of F. gigantica. In S. mansoni, actin was localized in similar tissues except the syncytium was not stained while spines exhibited intense staining. In F. gigantica, the presence of microtubules and actin filaments in the tegumental cells, their processes and in the syncytium could mediate the movement of secretory granules from the cell bodies towards the basal as well as the apical layer of the tegument. Cytokeratin filaments may serve to reinforce the integrity of the tegumental syncytium as well as the spines.

Invertebrate Muscles: Muscle Specific Genes and Proteins

This is the first of a projected series of canonic reviews covering all invertebrate muscle literature prior to 2005 and covers muscle genes and proteins except those involved in excitation-contraction coupling (e.g., the ryanodine receptor) and those forming ligand- and voltage-dependent channels. Two themes are of primary importance. The first is the evolutionary antiquity of muscle proteins. Actin, myosin, and tropomyosin (at least, the presence of other muscle proteins in these organisms has not been examined) exist in muscle-like cells in Radiata, and almost all muscle proteins are present across Bilateria, implying that the first Bilaterian had a complete, or near-complete, complement of present-day muscle proteins. The second is the extraordinary diversity of protein isoforms and genetic mechanisms for producing them. This rich diversity suggests that studying invertebrate muscle proteins and genes can be usefully applied to resolve phylogenetic relationships and to understand protein assembly coevolution. Fully achieving these goals, however, will require examination of a much broader range of species than has been heretofore performed.

Observations on the musculature and isolated muscle fibres of the liver fluke, Fasciola hepatica

The liver fluke, Fasciola hepatica relies on a well-developed muscular system, not only for attachment, but for many aspects of its biology. Despite this, little is known about the system beyond the gross organization of the main somatic muscle layers. In the present study, a range of techniques have been applied to F. hepatica in order to understand more about various aspects of muscle organization, biochemistry (in terms of muscle proteins) and identity of isolated muscle fibres. Scanning electron microscopy has provided a direct visualization in situ of the somatic muscle layers and the organization of the muscle fibres within the ventral sucker. The muscle bundles contributing to the main somatic muscle layers are made up of up to 10 individual muscle fibres. Phalloidin staining for actin, in conjunction with confocal microscopy, confirmed the presence of 2 main somatic muscle layers (outer circular, inner longitudinal), beneath which lies a third layer of oblique muscle fibres. The use of propidium iodide in combination with phalloidin staining for actin demonstrated that the cell bodies associated with the 2 main somatic muscle layers are situated beneath the longitudinal muscle layer and are connected to their respective muscle fibres by short cytoplasmic processes. Myosin immunoreactivity was demonstrated in the somatic muscle layers and in the muscle layers surrounding various organ systems within the fluke. Double labelling for actin and myosin confirmed the co-localization of the 2 muscle proteins in the muscle fibres of the ventral sucker. Muscle fibres from the somatic muscle layers and the ventral sucker have been isolated and images obtained with phase-contrast microscopy and scanning electron microscopy. The muscle fibres contain actin and myosin, but lack a nucleus, the connection with the cell body having been broken during the isolation procedure.

Ultrastructure of the tegument of Saccocoelioides godoyi

The tegument of adult Saccocoelioides godoyi Kohn & Froes, 1986 (Digenea: Haploporidae), specimens of which were collected from the intestine of the freshwater fish, Leporinus friderici (Bloch, 1794) (Anostomidae) from the reservoir of Itaipu Hydroelectric Power Station, Parana State, Brazil, was studied by transmission electron microscopy. The tegument comprises an external anucleate layer, covered by a surface plasma membrane and associated glycocalyx. The surface layer is bound by the basal plasma membrane and contains spines, two types of inclusion bodies and mitochondria. Tegumental cell bodies are located beneath the surface musculature and contain a single nucleus, cytoplasm with rough endoplasmic reticulum, mitochondria, ribosomes, and inclusion bodies similar to those found in the external layer. Cytoplasmic strands connect the cell bodies to the external surface layer, suggesting that the inclusion bodies are produced in these cells and pass up into the syncytium, as is known for other digeneans from experimental evidence.

Ionic mechanisms underlying spontaneous muscle contractions in the liver fluke, Fasciola hepatica

Spontaneous contractions of liver fluke muscle were abolished in Ca(2+)-free saline and by 100 microM nifedipine and reduced by 5 mM cadmium chloride, suggesting that they are dependent on extracellular Ca(2+). Caffeine (5 mM) significantly increased contraction amplitude and frequency. Ryanodine (100 microM) failed to block the caffeine response but significantly reduced spontaneous contraction frequency, suggesting that intracellular stores have a functional role. Cyclopiazonic acid (5 microM) had no effect on the caffeine response or spontaneous activity. 3-Isobutyl-1-methylxanthine (IBMX), forskolin, and 8-bromoadenosine 3',5'-cyclic monophosphate significantly increased spontaneous contractions, which implies that cAMP has a regulatory function in motility. Caffeine, however, produced no measurable increase in cAMP. The caffeine effect was inhibited by cadmium chloride and nifedipine, whereas IBMX-induced increases in amplitude were reduced by cadmium chloride. Thus caffeine and cAMP appear capable of opening plasma membrane Ca(2+) channels, but the involvement of cAMP in caffeine responses has not been proved.

Three main patterns in the expression of six actin genes in the plerocercoid and adult Diphyllobothrium dendriticum tapeworm (Cestoda)

The expression of six actin genes was examined in adult and plerocercoid Diphyllobothrium dendriticum tapeworms using in situ hybridization. On the basis of their structures, these genes are divided into three groups, the cestoda-I, -II and -III actins. Current studies show that the expression of actins belonging to different groups vary to a great extent. The three cestoda-I actins are expressed primarily in muscle cells of both adult and plerocercoid tapeworms, the expression being restricted to fewer cells in the plerocercoid larva. The two cestoda-II actins are cytoplasmic actin isoforms, expressed in a variety of cells, i.e. in cells dividing, differentiating and migrating. Expression of the cestoda-III actin gene is detected merely in the peripheral part of the outer parenchyma, mainly in the tegument cell bodies. This pattern is very weak in plerocercoids. The results indicate that actins also in D. dendriticum can be divided into cytoplasmic and muscle-specific isoforms. In this organism, one major pattern of muscle actin gene expression (cestoda-I) and two major patterns of non-muscle actin gene expression (cestoda-II and -III) were found.

Ultrastructural observations of the tegument of Postorchigenes gymnesicus (Digenea: Lecithodendriidae)

The tegument of Postorchigenes gymnesicus has been studied by scanning and transmission electron microscopy. The general body tegument is spinous and contains mitochondria, biconcave disc-shaped vesicles bounded by an unitary membrane and displaying a protein content, and scarce spherical bodies. The tegument covering specialized body regions is aspinous. Few vesicles were evident in the tegument covering the suckers and oesophagus, being more abundant in the metraterm and cirrus where the tegument is thicker. Laurer's canal has a thick tegument with sparse vesicles, mostly arranged close to the apical membrane. A direct association was evident between the basal lamina underlying the spines and the muscular subtegumental fibres, suggesting a motile character for the spine.

Actin isoforms in the parasitic nematode Haemonchus contortus

Actin proteins in the parasitic nematode Haemonchus contortus were partially purified by a new method based on precipitation with podophyllotoxin and dimethylsulfoxide. Two-dimensional gel electrophoresis of partially purified actin proteins revealed differences in isoform composition between adults and third-stage larvae. The significance of this finding is possibly related to the existence of differential functional or developmental characteristics between these two life-cycle stages.

Effects of luxabendazole on the tegument of Fasciola hepatica

The effects in vivo of 5, 10, and 20 mg/kg of luxabendazole (LBZ) on the tegument of Fasciola hepatica have been examined 48 h, 7 days and 14 days post-treatment of experimentally-infected rats. As early as 48 h post-treatment, the drug is shown to provoke significant damage to the tegument. The pathological phenomena characterizing LBZ damage are blebbing of the apical plasmalemma, formation of microvillus-like projections over the free surface, swelling of the basal infolds and stimulation of autophagy. The spines are often fractured; the tegument in the vicinity of spines seems more strongly altered than that in other foci. The basal layer is often changed, from increase of electron density to lack of integrity with the apical cytoplasm. The progress of the ultrastructural damage with time is not expressed. However, cytochemical data show that a longer post-treatment intervals the surface-coat structure becomes irregular and patches of ruthenium red positive material of variable thickness are focally accumulated. Only a slight dose-effect is noted 48 h after LBZ application when the alterations provoked by 5 mg/kg are less evident than those by 10 and 20 mg/kg.

Fasciola hepatica: localization and partial characterization of tubulin

The localisation and distribution of the cytoskeletal protein tubulin in the adult liver fluke Fasciola hepatica have been determined by an indirect immunofluorescence technique using a monoclonal antibody raised against beta-tubulin. Tubulin was demonstrated in the tegumental syncytium and in the tegumental cell bodies and their cytoplasmic connections with the surface syncytium. Immunostaining was also evident in the nerve fibres innervating sensory receptors in the tegument, in the nerve plexus innervating the sub-tegumental musculature and in the cytoplasmic extensions of the nurse cells within the vitelline follicle. Immunoblotting of whole fluke fractions produced a single band corresponding to a molecule of approximately 54 kDa in size. This figure corresponds with previous data obtained on tubulin from other helminth and eukaryotic sources.

Fasciola hepatica: the effect of the microfilament inhibitor cytochalasin B on the ultrastructure of the adult fluke

The effect of the microfilament inhibitor cytochalasin B (10 and 100 micrograms/ml) on the ultrastructure of adult Fasciola hepatica was determined in vitro by scanning and transmission electron microscopy (SEM, TEM) using both intact flukes and tissue-slice material. SEM revealed that initial swelling of the tegument led to surface blebbing and limited areas of sloughing after 24 h treatment at 100 micrograms/ml. In the tegumental syncytium, basal accumulations of secretory bodies (especially T2s) were evident in the earlier time periods but declined with longer incubations, until few secretory bodies remained in the syncytium overall. Blebbing of the apical plasma membrane and occasional areas of breakdown and sloughing of the tegument were observed over longer periods of treatment at 100 micrograms/ml. In the tegumental cell bodies, the Golgi complexes gradually decreased in size and activity, and few secretory bodies were produced. In the later time periods, the cells assumed abnormal shapes, the cytoplasm shrinking in towards the nucleus. In the vitelline follicles, a random dispersion of shell protein globules was evident within the intermediate-type cells, rather than their being organized into distinct shell globule clusters. Disruption of this process was more severe at the higher concentration of 100 micrograms/ml and again was more evident in tissue-slice material. In the latter, after prolonged (12 h) exposure to cytochalasin B, the intermediate and mature vitelline cells were filled with loosely packed and expanded shell globule clusters, containing few shell protein globules. The mature vitelline cells continued to lay down "yolk" globules and glycogen deposits. Disruption of the network of processes from the nurse cells was evident at the higher concentration of cytochalasin. Spaces began to appear between the vitelline cells and grew larger with progressively longer incubation periods, and the cells themselves assumed abnormal shapes. A number of binucleate stem cells were observed in tissue-slice material at the longest incubation period (12 h).