Biomedical subjects

G P Brennan

Publications and source records attributed to G P Brennan.

At least 19 recordsLinked to original sources

PubMed2006

Fasciola hepatica: ultrastructural effects of a combination of triclabendazole and clorsulon against mature fluke.

A study has been carried out to investigate the ultrastructural effects of triclabendazole (TCBZ) at half-normal concentration, clorsulon at half-normal concentration, and a combination of these two drugs against mature Fasciola hepatica. The Cullompton TCBZ-susceptible isolate was used for these experiments. Flukes were incubated for 24 h in vitro in TCBZ sulphoxide (7.5 microg/ml), clorsulon (5 microg/ml), or a combination of the two drugs. For the in vivo experiment, rats were dosed with TCBZ (5 mg/kg body weight), clorsulon (5 mg/kg body weight), or a combination of the two drugs, and flukes recovered after 48 h. Fine structural changes within the tegumental syncytium and tegumental cells were assessed by transmission electron microscopy. Treatment with the combination of drugs produced greater disruption to the flukes than the individual drugs at half-normal concentrations, both in vivo and in vitro; also than TCBZ.SO at normal concentration in vitro. The changes observed aid in the understanding of the gross changes to the tegumental surface described previously (Meaney M, Allister J, McKinstry B, McLaughlin K, Brennan GP, Forbes AB, Fairweather I. Parasitol Res 99:609-621, 2006). The results indicate that there are additive effects between TCBZ and clorsulon and suggest that the use of drug combinations would be of value in the treatment of TCBZ-resistant fluke.

Animals↗

PubMed2006

Immature triclabendazole-resistant Fasciola hepatica: tegumental responses to in vitro treatment with the sulphoxide metabolite of the experimental fasciolicide compound alpha.

Juvenile triclabendazole-resistant liver flukes, Fasciola hepatica, were incubated in vitro with 10 microg/ml of the sulphoxide metabolite of the experimental fasciolicide, compound alpha [5-chloro-2-methylthio-6-(1-naphthyloxy)-1H-benzimidazole], for 6 and 18 h. Following treatment, the specimens were examined using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and tubulin immunocytochemistry. The SEM results revealed a posterior-directed disruption comprised predominantly of swelling and blebbing of the tegument; these changes were more severe and extensive after the longer 18-h incubation. Along with swelling of the tegument and blebbing, the TEM results also revealed swelling of the mitochondria and basal infolds. A decrease in the number of both T1 and T2 secretory bodies was observed in the syncytium and cytoplasmic connections after the 18-h treatment. The circular muscle bundles were also disrupted, in that the organisation of the muscle fibres was irregular and the total number of muscle fibres was reduced. The immunocytochemical studies revealed no significant disruption to the distribution of tubulin immunoreactivity within the tegumental syncytium, the cytoplasmic connections or the associated tegumental cells. The results indicate that alpha.SO is capable of disrupting the tegument of 4-week-old triclabendazole-resistant liver flukes, though the morphological changes were not associated with any significant differences in tubulin immunostaining.

Animals↗

PubMed2006

Eukaryotic expression of recombinant Pso o 1, an allergen from Psoroptes ovis, and its localization in the mite.

A cDNA encoding the immunogen Pso o 1 from Psoroptes ovis was obtained by polymerase chain reaction (PCR) amplification. The amplicon contained the entire coding sequence for the prepro-enzyme in an open reading frame (ORF) of 966 bp. This gene encoded a predicted protein of 322 amino acids (aa) with 64% aa identity (80% similarity) to the major house dust mite faecal allergen Der f 1. The pro-enzyme form of Pso o 1 was expressed as a recombinant protein in the Pichia pastoris-eukaryotic expression system. Maturation of the recombinant pro-enzyme by autocatalytic activation was not observed, and such maturation could not be achieved using a number of techniques known to activate recombinant Der p 1 and Der f 1 expressed in the same system. Serum raised against recombinant Pso o 1 cross-reacted with mature Der p 1 and allowed Pso o 1 to be immunolocalized to the gut of P. ovis.

Allergens↗

PubMed2006

Fasciola hepatica: morphological effects of a combination of triclabendazole and clorsulon against mature fluke.

A study has been carried out to investigate the morphological effects of half-strength triclabendazole (TCBZ), half-strength clorsulon, and a combination of these two drugs against mature Fasciola hepatica. The Cullompton TCBZ-susceptible isolate was used for these experiments. Flukes were incubated for 24 h in vitro in TCBZ sulphoxide (7.5 microg/ml), clorsulon (5 microg/ml), or a combination of the two drugs. For the in vivo experiment, rats were dosed with TCBZ (6.25 mg/kg body weight), clorsulon (5 mg/kg body weight), or a combination of the two drugs and flukes recovered after 48 h. Surface changes to the flukes were assessed by scanning electron microscopy. Treatment with the combination of drugs produced greater disruption to the flukes than the individual drugs at half-strength, both in vivo and in vitro. Disruption to the tegument of the flukes induced by the individual drugs at half-strength was relatively minor and less than that caused by the drugs at full-strength. The results suggest that there are additive effects between TCBZ and clorsulon, which may be indicative of synergy: the use of drug combinations would be of value in the treatment of triclabendazole-resistant fluke.

Animals↗

PubMed2006

Molecular characterization, expression and localization of tropomyosin and paramyosin immunodominant allergens from sheep scab mites (Psoroptes ovis).

cDNAs encoding the immunodominant allergens tropomyosin and paramyosin were amplified from RNA extracted from the sheep scab mite Psoroptes ovis. The tropomyosin cDNA contained an open reading frame (ORF) of 852 bp which encoded a predicted protein with 98% and 97% identity to the house dust mite allergens Der f 10 and Der p 10 respectively. The complete paramyosin ORF generated by RT-PCR was 2625 bp in length and encoded an 875aa predicted protein of 102.6 kDa with 97%, 95% and 89% identity to the paramyosins of Dermatophagoides pteronyssinus (Der p 11), Sarcoptes scabiei and Blomia tropicalis (Blo t 11) respectively. Full length tropomyosin and truncated and full-length paramyosin were expressed as recombinant proteins. IgG and IgE in sera from sheep with a 6-week duration primary infestation of P. ovis did not detect either full-length or truncated recombinant paramyosin. IgG in both infested and naïve sheep sera detected recombinant tropomyosin, suggesting cross-reactivity to tropomyosin and to other invertebrate species to which the sheep may have been exposed. Staining with antibodies directed against tropomyosin and paramyosin was observed throughout sections of P. ovis. Staining was especially prevalent in the anterior sections of the mites, possibly associated with locomotory muscles in this region.

Allergens↗

PubMed2006

Adult triclabendazole-resistant Fasciola hepatica: surface and subsurface tegumental responses to in vitro treatment with the sulphoxide metabolite of the experimental fasciolicide compound alpha.

Mature Fasciola hepatica of the triclabendazole-resistant Sligo isolate were incubated in vitro with 10 microg/ml of the sulphoxide metabolite of compound alpha [5-chloro-2-methylthio-6-(1-naphthyloxy)-H-benzimidazole]; the metabolite will be referred to as alpha.SO. Changes resulting from drug treatment were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and tubulin immunocytochemistry (ICC). SEM revealed that disruption to the tegumental surface mainly took the form of swelling and blebbing. Extensive spine loss occurred on the ventral surface of the oral cone, and sloughing of the tegument was observed along the lateral margins of the fluke. Examination of sections from the anterior mid-body region at the TEM level revealed that treatment with alpha.SO led to swelling of the basal infolds and mitochondria within the tegumental syncytium; also, accumulations of secretory bodies beneath the apical plasma membrane. The tegumental cell bodies contained swollen mitochondria and cisternae of granular endoplasmic reticulum, but few Golgi complexes were observed. An increase in T2 secretory bodies was observed, whilst in the T1 tegumental cells, the T1 secretory bodies had decreased in number. Immunocytochemical (ICC) studies showed that incubation with alpha.SO, ABZ.SO and TCBZ.SO did not cause significant changes to the distribution of tubulin within the tegumental syncytium of the Sligo isolate. In contrast, alpha.SO, ABZ.SO and TCBZ.SO caused severe disruption to tubulin organization within the syncytial layer of the TCBZ-susceptible Cullompton isolate. The EM results confirm that compound alpha is a fasciolicide capable of disrupting the tegument of mature TCBZ-resistant F. hepatica; however, this was not accompanied by any change in tubulin immunoreactivity.

Animals↗

PubMed2005

Fine structure of the anterior adhesive apparatus (head organs) of Bravohollisia gussevi Lim, 1995 (Monogenea: Ancyrocephalidae).

A study of the anterior adhesive apparatus (head organs) of Bravohollisia gussevi Lim, 1995 was carried out using light and electron microscopy. The anterior adhesive apparatus or head organs in B. gussevi comprise 6 circular openings or apertures in the antero-lateral region, associated pits lined with specialized microvillous tegument that differ from the general body tegument, a bundle of ducts, and uninucleate gland cells located lateral to the pharynx. The uninucleate glands of the anterior adhesive apparatus (head organs) comprise 2 types of cells, one kind of cell producing rod-like bodies (S1) and the other oval bodies (S2). The S1 bodies are filled with numerous, less electron-dense vesicles in an electron-dense matrix, while S2 bodies have no vesicles but contain a more homogeneous electron-dense matrix. Interlinking band-like structures were observed between S1 bodies. Similar band-like structures were found between S2 bodies. The formation of S1 bodies was followed by transmission electron microscopy. However, the formation of S2 bodies was unclear and could not be resolved. Uniciliated structures were also observed around the openings of the anterior adhesive apparatus. Each uniciliated structure is usually associated with an opening of a gland cell producing granular, electron-dense, secretory bodies, which differ from the secretions produced by the lateral gland cells of the anterior adhesive apparatus.

Animal Structures↗

PubMed2005

Ultrastructural observations on oral ingestion and trans-tegumental uptake of clorsulon by the liver fluke, Fasciola hepatica.

Three experiments have been carried out in vitro to determine the effect of oral and trans-tegumental uptake of clorsulon on the fine structure of the tegument and gut of Fasciola hepatica. Changes were assessed by transmission electron microscopy. In the first experiment, the flukes were ligatured to prevent the oral ingestion of drug and treated for 24 h in clorsulon (10 microg/ml). Limited swelling of the basal infolds was observed in the tegumental syncytium. Swollen mitochondria were present in the syncytium, the underlying tegumental cells and in the gastrodermal cells. Swelling and vesiculation of the cisternae of the granular endoplasmic reticulum (ger) was evident in the gastrodermal cells, together with a reduction in secretory activity. In the second experiment, flukes were fed for 24 h on red blood cells isolated from rats dosed with clorsulon at 12.5 mg/kg body weight; this experiment was designed to prevent the exposure of the tegumental surface to the drug. There was severe swelling of the basal infolds in the tegumental syncytium and swelling of mitochondria in the syncytium, tegumental cells and gastrodermal cells. In the tegumental cells there was a decrease in the number of Golgi complexes as well. A number of changes were evident in the gastrodermal cells: swelling of the ger cisternae, an increase in the number of autophagic vacuoles, a reduction in the number of secretory bodies and disruption of the lamellae projecting from the surface of the cells. In the third experiment, flukes were incubated for 24 h in clorsulon (10 microg/ml), with both absorptive surfaces being available for drug uptake. There was severe swelling of the basal infolds in the tegumental syncytium and large autophagic vacuoles were present. Swollen mitochondria were a feature of the tegument, tegumental cells and gastrodermal cells, as were swollen cisternae of ger in the tegumental and gastrodermal cells. Fewer Golgi complexes were observed in the tegumental cells and in the gastrodermal cells there were fewer secretory bodies and an increased number of autophagic vacuoles. Overall, the gastrodermal cells were more severely affected than the tegument. Greater disruption of the tegument occurred when the oral route of uptake was available. The results support those of previous studies which point to oral uptake of clorsulon being the major route of entry into the fluke.

Administration, Oral↗

PubMed2004

A scanning electron microscope study on the route of entry of clorsulon into the liver fluke, Fasciola hepatica.

Three experiments were carried out in vitro to determine the roles of the tegument and gut of Fasciola hepatica in the uptake of the flukicidal drug, clorsulon. Changes to the two surfaces were assessed by scanning electron microscopy. In the first experiment, the flukes were ligatured to prevent the oral ingestion of drug and treated for 24 h in clorsulon (10 microg/ml). The gastrodermal surface remained normal and few changes to the tegumental surface were observed. In the second experiment, flukes were fed for 24 h on red blood cells isolated from rats dosed with clorsulon at 12.5 mg/kg body weight; this experiment was designed to prevent the exposure of the tegumental surface to the drug. The gastrodermal surface was severely disrupted and the gut lamellae were disorganised and necrotic. Swelling of the tegument and blebbing on the tegumental surface were evident, but the changes were not severe. More severe swelling of the tegument was observed in the third experiment, in which flukes were incubated for 24 h in clorsulon (10 microg/ml), with both absorptive surfaces being available for drug uptake. The gastrodermal surface was badly disrupted and the gut lamellae were disorganised and necrotic. Taking the results of the three experiments together, the gastrodermal surface was more affected than the tegument and the greatest disruption to the two surfaces was seen when both routes of entry were available to the fluke. The data support a previous study which indicated that entry of clorsulon into the fluke in vivo is principally by the oral ingestion of drug bound to the red blood cells.

Animals↗

PubMed2004

Response of two isolates of Fasciola hepatica to treatment with triclabendazole in vivo and in vitro.

In this study, the susceptibility of two isolates of Fasciola hepatica--the Fairhurst and Oberon isolates--to treatment with triclabendazole was investigated, both in vivo and in vitro. The Fairhurst isolate originated in England, but has since been maintained in Australia; the Oberon isolate originated in Australia. Triclabendazole had a very high efficacy against the Fairhurst isolate. In sheep (dose: 10 mg/kg), the efficacy ranged from 78.4% at 2 weeks post-infection to 98.5% at 6 weeks post-infection. In cattle (dose: 12 mg/kg) efficacy was 89% at 2 weeks post-infection and 100% at 12 weeks. In contrast, against the Oberon isolate, triclabendazole had 0% efficacy against 2-week-old flukes in sheep (dose: 10 mg/kg) and 5% against 4-week-old flukes. Surface changes to flukes of the two isolates were assessed by scanning electron microscopy following treatment in vitro for 24 h in triclabendazole sulphoxide (15 and 50 microg/ml). Disruption took the form of blebbing, swelling and furrowing of the tegument and was greater in the Fairhurst than the Oberon isolate. Surface changes generally were more severe in the anterior than posterior region of the fluke and the dorsal surface was also consistently more severely affected than the ventral surface. Disruption was more severe at the higher drug concentration for both isolates. The morphological data is consistent with the efficacy data, which indicates that the Fairhurst isolate of F. hepatica is susceptible to triclabendazole treatment, whilst the Oberon isolate is refractory.

Animals↗

PubMed2004

Transmission electron microscope study of the ultrastructural changes induced in the tegument and gut of Fasciola hepatica following in vivo drug treatment with clorsulon.

Using transmission electron microscopy (TEM), both the tegument and gut of Fasciola hepatica were examined in an effort to identify and characterise the ultrastructural changes induced following treatment with the flukicidal drug clorsulon. Male Sprague-Dawley rats infected with F. hepatica were dosed orally at 8-8.5 weeks post-infection with clorsulon at a concentration of 12.5 mg/kg body weight. After 24, 48 and 72 h, rats were sacrificed by cervical dislocation and mature flukes recovered from the bile ducts. After 24 h treatment in vivo, disruption of the tegumental syncytium was concentrated at the apex of the syncytium where a dark band consisting of numerous secretory bodies was present. Some blebbing of the apex had also occurred, "open" bodies were present in this region and the mitochondria were slightly swollen. In the cell bodies, swelling of the mitochondria and their cristae had also occurred and the Golgi complexes appeared to be smaller than normal. The disruption seen after 48 h treatment in vivo was similar but more severe: the frequency of blebbing had increased, as had the number of "open" bodies and the swelling of the mitochondria. Vacuoles had begun to appear in the syncytium-both autophagic and electron-lucent-and swelling of the mucopolysaccharide masses around the basal infolds had occurred. Lipid droplets were observed occasionally. In the cell bodies, autophagic vacuoles had begun to appear and swelling of the mitochondria had increased in severity. After 72 h treatment in vivo, more severe disruption was seen in the tegumental syncytium in which widespread swelling and blebbing of the apex was apparent. The basal infolds had become very badly swollen in a number of specimens and damage to the spines was evident. The mitochondria remained swollen, as did the mucopolysaccharide masses around the basal infolds. Lipid droplets were more frequently observed in the syncytium. In the tegumental cells, swelling of the mitochondria was greater and an increase in the number of autophagic vacuoles was apparent. The gut showed signs of disruption after 24 h treatment in vivo, in that the surface lamellae were disrupted and a build-up of autophagic vacuoles at the apex of the cells had taken place. Swelling of the mitochondria and the cisternae of granular endoplasmic reticulum (gER) was evident. There was a decrease in the number of secretory bodies. After 48 h treatment in vivo, the number of autophagic vacuoles in the gastrodermal cells had increased, the mitochondria and gER remained swollen and the disruption seen to the lamellae was still evident. In the 72 h-treated specimens, the disruption seen in the gastrodermal cells had increased significantly, with severe vacuolation of the apical cytoplasm. An increase in the number of autophagic vacuoles was evident, the mitochondria and the gER remained swollen and lipid droplets were present in the cells.

Animals↗

PubMed2003

Fasciola hepatica: effects of the fasciolicide clorsulon in vitro and in vivo on the tegumental surface, and a comparison of the effects on young- and old-mature flukes.

The ultrastructural changes in Fasciola hepatica induced by the fasciolicide clorsulon were assessed using scanning electron microscopy. At 8 and 44 weeks post-infection, male Sprague-Dawley rats infected with F. hepaticawere dosed orally with clorsulon at a concentration of 12.5 mg/kg and mature flukes recovered from the bile duct after 24 h, 48 h, and 72 h in both experiments. An in vitro incubation was also set up using mature fluke (8 weeks old) incubated with clorsulon for 24 h at a concentration of 10 microg/ml. After 24 h in vivo, the young-mature flukes (8 weeks old) showed significant disruption to the tegumental surface, particularly in the anterior mid-body region, where a distinct band of swelling and blebbing was evident. The band began just behind the ventral sucker and ran posteriorly along both margins. The apical cone region of the fluke was characterised by swelling and blebbing of the surface between the spines. Similar changes were evident after 48 h in vivo, but the disruption was more severe and the mid-body band had spread posteriorly. In approximately half of the specimens recovered after 72 h in vivo, widespread disruption had occurred, with sloughing of the apical membrane or the entire syncytium, over almost all of the oral cone and anterior mid-body. For all time periods, the anterior half of the fluke was more severely affected than the posterior half. No differences were seen between the dorsal and ventral surfaces. Old-mature flukes (44 weeks old) showed regionally similar, but more severe and widespread disruption than that seen in the young-mature flukes. The onset of surface changes occurred more quickly in old-mature flukes as well. Eight-week-old flukes which had been incubated for 24 h in vitro showed surprisingly little disruption, but this may be due to the method by which the drug is taken up by the fluke.

Animals↗

PubMed2003

Fasciola hepatica: tegumental surface alterations following treatment in vivo and in vitro with nitroxynil (Trodax).

Male Sprague-Dawley rats were dosed orally with nitroxynil at a concentration of 40 mg/kg and adult Fasciola hepatica recovered after 24 h, 48 h and 72 h. Surface changes to the flukes were monitored by means of SEM. After the 24 h treatment, extensive swelling and blebbing of the tegument was observed on both surfaces, although the dorsal anterior region was more severely affected than either the posterior dorsal region or entire ventral surface. At high magnification, microvillus-like projections were evident, giving the surface a roughened appearance. After 48 h, the changes evident at 24 h had become more severe and some tegumental loss had occurred in the oral region of the fluke. Surface disruption was particularly evident along the lateral margins of the fluke in this region. In some specimens a single large swelling was present in the dorsal midbody region. The swelling was a more typical feature of flukes recovered. After 72 h, tegumental loss was more widespread, occurring over the oral cone and anterior midbody on the dorsal surface. Overall the dorsal surface was consistently more severely affected than the ventral surface, and the anterior region of the fluke was more disrupted than the posterior region. After 24 h in vitro incubation, the oral cone and midbody exhibited considerable spine loss and swelling. Overall, the dorsal surface was more disrupted than the ventral surface and the anterior region of the fluke was more disrupted than the posterior region. Regional differences in the response of the fluke to nitroxynil will be compared to previously published data with other fasciolicides. The results indicate that the tegument is an important target for nitroxynil action. Disruption of this, the fluke's main line of defence, would allow the drug access to other internal tissues, leading to more widespread damage.

Animals↗

PubMed2002

Fasciola gigantica: tegumental surface alterations following treatment in vitro with the sulphoxide metabolite of triclabendazole.

The effect of the active sulphoxide metabolite of the fasciolicide triclabendazole on the surface morphology of the tropical liver fluke, Fasciola gigantica, was determined in vitro by scanning electron microscopy. At a concentration of 10 microg/ml, swelling and blebbing of the tegument was evident after only 6 h incubation. The blebbing was focussed on the spines. With progressively longer incubation periods, blebbing on the spines became more severe, leading to tegumental sloughing and spine loss. Tegumental loss became more widespread and, after incubation periods of 18 h and 24 h in vitro, perforations of the basal lamina were evident and, in some cases, holes penetrated through the entire fluke in the tail region. The ventral surface was consistently more severely affected than the dorsal and similarly the posterior region of the fluke was more disrupted than the anterior region. The results confirm the potent activity of triclabendazole against F. gigantica.

Animals↗

PubMed2001

Immunomicroscopical observations on the nervous system of adult Eudiplozoon nipponicum (Monogenea: Diplozoidae).

Neuronal pathways have been examined in adult Eudiplozoon nipponicum (Monogenea: Diplozoidae), using cytochemistry interfaced with confocal scanning laser microscopy, in an attempt to ascertain the status of the nervous system. Peptidergic and serotoninergic innervation was demonstrated by indirect immunocytochemistry and cholinergic components by enzyme cytochemical methodology; post-embedding electron microscopical immunogold labelling revealed neuropeptide immunoreactivity at the subcellular level. All three classes of neuronal mediators were identified throughout both central and peripheral elements of a well-differentiated orthogonal nervous system. There was considerable overlap in the staining patterns for cholinergic and peptidergic components, while dual immunostaining revealed serotonin immunoreactivity to be largely confined to a separate set of neurons. The subcellular distribution of immunoreactivity to the flatworm neuropeptide, GYIRFamide, confirmed neuropeptide localisation in dense-cored vesicles in the majority of the axons and terminal varicosities of both central and peripheral nervous systems. Results reveal an extensive and chemically diverse nervous system and suggest that pairing of individuals involves fusion of central nerve elements; it is likely also that there is continuity between the peripheral nervous systems of the two partner worms.

Animals↗

PubMed2001

Development of the vitellaria of the liver fluke, Fasciola hepatica in the rat host.

The development of the vitellaria of Fasciola hepatica within the liver of its rat host was studied by means of whole-mount stained preparations and transmission electron microscopy, together with light and electron immunocytochemistry using an antibody to vitelline protein B, an eggshell precursor protein synthesized by F. hepatica. No vitelline cells could be identified in flukes recovered from the liver parenchyma, by any of the methods used. In contrast, follicles were present in flukes at the earliest time of recovery from the bile duct, namely, 5 weeks 3 days post-infection. The vitellaria in these flukes formed a row of small follicles on either side of the body. Development of the follicles was rapid: by 6 weeks 3 days, the vitellaria resembled those in the adult fluke and eggs were present in the uterus. Immunolabelling was confined to the shell protein globules in the vitelline cells, confirming the packaging of the eggshell protein within the shell globule clusters.

Animals↗

PubMed2000

Ultrastructure of the surface structures and haptor of Empleurosoma pyriforme (Ancyrocephalinae; Monopisthocotylea: Monogenea) from the gills of the teleost fish Therapon jarbua.

Infections with Empleurosoma pyriforme occur between successive secondary gill lamellae on both sides of the primary lamella of Therapon jarbua. The haptoral disc bears two pairs of anchors and a pair of connecting transverse bars. The attachment of the parasite to the host gill causes inflammation, erosion and degeneration of the gill epithelia. The ventral anchors consist of an inner core of irregularly arranged, electron-dense fibrils and a smooth outer core of electron-lucent fibrils, whereas the surface of the dorsal anchors is ridged. Both the dorsal and the ventral anchors may be extended or withdrawn. The connecting transverse bars consist of longitudinally arranged fibrils in an electron-dense matrix, whereas the tendons consist of fibrils, supported in a less electron-dense matrix, which interconnect the anchor erector-protractor muscles and the haptor muscles. Two types of perikarya are present. The less common type contain large multivesicular bodies and small electron-dense granules and are located only in the haptor region. The second and more common perikarya are present throughout the body surface. The cytoplasmic syncytium contains numerous electron-dense granules and electron-lucent vesicles. Beneath the syncytium, unicellular epidermal gland cells contain electron-dense granules. Neurones containing numerous electron-dense vesicles are present in the haptor region. Uniciliate presumed sensory receptors are distributed over the body surface. Groups of ciliated sensory structures are present in the forebody. Ciliated and non-ciliated presumed sensory receptors are present in the sleeve cavity of the anchors, on the haptor and in the vicinity of the oral apertures.

Animals↗

PubMed1998

Observations on the mechanism of eggshell formation in the liver fluke, Fasciola hepatica.

A mechanism for eggshell production in Schistosoma mansoni has been proposed (Wells & Cordingley, 1991), and suggests that the release of eggshell protein globules from the vitelline cells occurs under alkaline conditions within the ootype followed by their subsequent fusion to form the eggshell. Fusion and tanning of these components produces eggshell which autofluoresces. The present study was carried out to determine whether a similar process operates in Fasciola hepatica. A number of drug treatments were used to disrupt key steps in the maturation of vitelline cells. Treatment with the calcium ionophore lasalocid (1 x 10(-5) M) led to the premature release of eggshell globules from the vitelline cells but not their fusion. Incubation in monensin (1 x 10(-6)M), a sodium ionophore and ammonium chloride (NH4Cl) (5 x 10(-2) M), a weak base, resulted in the premature fusion of eggshell protein globules within the vitelline cells and premature tanning of the eggshell protein material. The copper-containing enzyme, phenol oxidase, is thought to be involved in the tanning process during the production of eggs. Diethyldithiocarbamate, (DDC, 1 x 10(-3) M) is a phenol oxidase inhibitor and treatment with this compound, in combination treatments with monensin and NH4Cl, prevented fusion of the vitelline cell globules and tanning of the shell protein material. The results of the study suggest that the mechanism for eggshell formation in F. hepatica is similar to that proposed for S. mansoni and may be common to other trematodes as well.

Ammonium Chloride↗