bluuebunny/crossref_metadata_2025 huggingface dataset:
Lymphoreticular responses to metacestodes: Taenia multiceps (Cestoda) can modify interaction between accessory cells and responder cells during lymphocyte activation
Authors: Rakha N. K. , Dixon J. B. , Skerritt G. C. , Carter S. D. , Jenkins P. , Marshall-Clarke S.
Published: June 2009

This study was designed to test the accessory function of macrophages after activation with products of Taenia multiceps coenuri. Activation was carried out by intraperitoneal injection of mice with coenurus fluid or protoscolex culture supernatant, and function was assessed by adding these macrophages in progressively increasing numbers to macrophage-depleted lymphocyte cultures transforming under the influence of plant mitogens or coenurus-fluid mitogen. In contrast to normal macrophages, which have a progressively enhancing action on the above reactions, parasite-activated macro-phages at similar concentrations were progressively inhibitory. However, low concentrations of the activated macrophages enhanced mitosis as well as, or better than, normal. Lymph node cells from injected mice showed abnormal response to macrophage-derived signals. In particular there was subnormal reaction to macrophages in the presence of coenurus mitogen. These results suggest that T. multiceps coenuri may survive in the host because of their ability to reduce effective interaction between lymphocytes and accessory cells.
Influence of larval schistosomes on polysaccharide synthesis in albumin glands of Biomphalaria glabrata
Authors: Crews A. E. , Yoshino T. P.
Published: June 2009

An in vitro bioassay was used to examine [14C]glucose incorporation into polysaccharides in albumen glands (AGs) of susceptible M-line Biomphalaria glabrata infected with the NMRI strain of Schistosoma mansoni. Polysaccharide and galactogen synthesis were unaffected by larval trematode infection in AGs of snails at days 14, 21, and 28 post-infection (p.i.) when compared to uninfected controls. Further experiments were conducted to determine if daughter sporocysts, hypothesized to be primary mediators of parasitic castration in this system, were able to exert direct effects on synthetic activity of uninfected AGs via haemolymph-borne molecules or in vitro culture-generated larval excretory–secretory (ES) products. When AGs were incubated in the presence of infected snail haemolymph, significant differences in quantities of polysaccharides and galactogen were detected only in test organs incubated in day 28 p.i. haemolymph. Daughter sporocyst ES products generated during the first 48 h of culture caused a significant reduction in polysaccharide and galactogen synthesis in test organs. When ES products from days 3 to 6 of in vitro culture were tested similarly, no significant differences in either polysaccharide or galactogen synthesis were observed between control and test organs. These data demonstrate that daughter sporocysts are able to modulate a specific aspect of the reproductive activity of the snail host through haemolymph-borne molecules of host or parasite origin, or directly through in vitro culture-generated ES products.
Evidence that the mechanism of gene exchange in Trypanosoma brucei involves meiosis and syngamy
Authors: Turner C. M. R. , Sternberg J. , Buchanan N. , Smith E. , Hide G. , Tait A.
Published: June 2009

All pairwise combinations of three cloned stocks of Trypanosoma brucei (STIB 247L, STIB 386AA and TREU 927/4) were co-transmitted through tsetse flies (Glossina morsitans) and screened for the production of hybrid trypanosomes. Clones of metacyclic and bloodstream trypanosomes from flies harbouring mature infections containing hybrid trypanosomes were established and screened for several isoenzyme and restriction fragment length polymorphisms. For each of the three combinations of parents, some progeny clones were observed to be of a phenotype and genotype indicating that genetic exchange had occurred during development of the trypanosomes in flies. These hybrid clones shared three salient features: (1) where the parents were homozygous variants the progeny were heterozygous, (2) where one of the parents was heterozygous, allelic segregation was observed and (3) the progeny clones were shown to be recombinant when two or more markers for which one of the parents was heterozygous were examined. These results are consistent with the progeny being an F1 in a diploid mendelian genetic system involving meiosis and syngamy. Our observations show that all possible combinations of the three stocks may undergo genetic exchange. A marker analysis of a series of clones each derived from single metacyclic trypanosomes showed that individual flies transmit a mixture of trypanosome genotypes corresponding to F1 progeny and to parental types, indicating that genetic exchange was a non-obligatory event in the life-cycle of the trypanosome. In addition, a preliminary analysis of the phenotype of procyclic stage trypanosomes derived from flies infected with two stocks, indicates that genetic exchange is unlikely to occur at this stage.
Fractionation and antigenic characterization of organelles ofEimeria tenellasporozoites
Authors: Kawazoe U. , Tomley F. M. , Frazier J. A.
Published: June 2009

Sporozoites ofEimeria tenellawere disrupted by sonication and subcellular fractions were separated by sucrose gradient ultracentrifugation. Fractions from gradients were characterized by electron microscopical appearance and their polypeptide and antigenic profiles determined by PAGE and Western blotting with antisera to sporozoites and 1st- and 2nd-generation merozoites. Fractions containing micronemes, rhoptries or membranes showed markedly different polypeptide content and antigenic reactivity. Microneme epitopes were strongly conserved between sporozoites and 2nd-generation merozoites whereas the majority of rhoptry epitopes and many membrane epitopes were sporozoite specific. The only polypeptide of sporozoites which was strongly recognized by antisera raised to 1st generation merozoites was a microneme antigen of molecular weight approximately 100 kDa.
Developmental changes of Echinococcus multilocularis metacestodes revealed by tegumental ultrastructure and lectin-binding sites
Authors: Leducq R. , Gabrion C.
Published: June 2009

Ultrastructural investigations (SEM, TEM) combined with lectin-binding analysis, have revealed concurrent modifications in tegumentary structure and surface glycoconjugates during the establishment and differentiation of Echinococcus multilocularis metacestodes in jirds. The laminated layer, which is amorphous and rich in polysaccharides when initially secreted by the young cyst, takes on a different appearance and has a different glycoconjugate composition according to whether the cyst becomes fertile or sterile. The laminated layer of fertile cysts transforms into a microfibrillar matrix, the protein content of which may increase while sugar content decreases during protoscolex differentiation. Independently of this structure, brood capsules, from which arise protoscoleces, are formed by invagination of the cyst tegument. The intense secretion of glycoconjugates from the brood capsule wall during invagination may serve to interact with host factors passing through the laminated layer. The combined use of ultrastructural study and lectin labelling has allowed the demonstration of an ultrastructural and biochemical gradient of differentiation of the protoscolex. Seven stages of differentiation have been described. The possibility that the excreted–secreted tegumentary glycoconjugates, revealed by lectin labelling during protoscolex differentiation, might be the gradual biochemical expression of one or several stimuli implicated in the phenomenon of protoscolex maturation, is discussed.
Segregation and co-occurrence of larval cestodes in freshwater fishes in the Bothnian Bay, Finland
Authors: Andersen K. I. , Valtonen E. T.
Published: June 2009

Two autogenic (Triaenophorus crassus and T. nodulosus) and four allogenic (Diphyllobothrium latum, D. dendriticum, D. ditremum and Schistocephalus solidus) larval cestode species were found in 13 out of 31 fish species studied from the Bothnian Bay, NE Baltic. Gasterosteus aculeatus was the most heavily infected fish with 4 larval cestode species; for two of them (D. ditremum and S. solidus) the three-spined stickleback was found to be the required fish intermediate host. Among allogenic cestode species, those restricted to different definitive host species segregated their larval population in relation to the fish host, while, for example, D. ditremum and S. solidus, both maturing in fish-eating birds, had the highest percentage of co-occurrences. D. dendriticum, which had the widest range of definitive hosts, was found in the greatest number (8) of fish species and co-occurred with all other species found except T. crassus. The two autogenic species totally segregated their larval population from each other although they both require pike as definitive host. The ecological and evolutionary relationships behind the patterns found for larval cestodes are discussed.
Species richness in helminth communities: the importance of multiple congeners
Authors: Kennedy C. R. , Bush A. O.
Published: June 2009

Using data sets derived from published literature, the contribution of congeneric species to helminth component community richness is evaluated. Consideration of the frequency distribution of congeners in relation to host and parasite groups reveals that the distributions are unimodal, that singletons are the commonest class and that the frequency of occurrence of congeners decreases with increasing number of species per genus. Congeners may be found in any group of hosts or parasites, but are more common amongst cestodes of aquatic birds. Two patterns of occurrence of congeneric species are recognized: one in which from a few to multiple congeners are found within a single helminth genus, exemplified by dactylogyrid monogeneans and cloacinid nematodes, and the other in which there is a simultaneous occurrence of congenerics and confamilials such that there are several genera involved, but each represented by fewer species, exemplified by strongyles in horses. The question of whether these patterns can be considered examples of species flocks is discussed. We conclude that multiple congeners and species flocks are interesting phenomena but, except in isolated cases, they make insignificant contributions to community richness.
Relationship between the production of interferon-α/β and interferon-γ during acute toxoplasmosis
Authors: Diez B. , Galdeano A. , Nicolas R. , Cisterna R.
Published: June 2009

Acute toxoplasmosis was induced in mice, and interferon (IFN) production in serum and by spleen cells was evaluated during the infection period. Interferon was characterized by acid-treatment and anti-IFN-α/β neutralization. In order to verify the correlation between the unusual aspects of the IFN production and the induction of immunosuppression, splenocyte mitogen responsiveness was investigated concomitantly to IFN synthesis. The activity ofToxoplasma-induced serum IFN-α/β increased gradually throughout all post-infection days, but IFN-γ was not detected in the systemic circulation at any time during the infection. It was also observed that IFN-α/β production and the capacity to produce IFN-γ by spleen cells were closely and inversely correlated. As the infection progressed, more IFN-α/β was produced, and the ability of spleen cells to produce IFN-γ decreased. The observation thatToxoplasma-infected mice were concomitantly immunosuppressed (as documented by mitogen unresponsiveness and defective IFN-γ production) in direct correlation to IFN-α/β production, suggests that such IFN-α/β production is an important factor associated with acute toxoplasmosis-induced immunosuppression.
Ancylostoma duodenale and Necator americanus: effect of temperature on egg development and mortality
Authors: Smith G. , Schad G. A.
Published: June 2009

The development and mortality of the eggs of Ancylostoma duodenale and Necator americanus in distilled water were monitored over a range of temperatures between 15 and 35°C. Egg demography was examined within the context of a fourparameter mathematical model of development and mortality. Over the range of temperatures studied, egg mortality (μ) was an increasing exponential function of temperature (T) measured in degrees Celsius. A single model adequately described the mortality of both species (ln [μ] = 0·041*T − 6·87). The minimum time (τ) to hatching was consistently less for A. duodenale (ln [1/T] = −(0·79+53·05*[l/T]) than N. americanus (ln [1/T] = −(0·99 + 53·05*[l/T])). The hatching rate [σ when t > τ) was an increasing function of time and temperature in both cases, but the precise functional relationship was species specific.
Commitment of the malaria parasite Plasmodium falciparum to sexual and asexual development
Authors: Bruce M. C. , Alano P. , Duthie S. , Carter R.
Published: June 2009

Blood-stage malaria parasites in the vertebrate host can develop either into the asexual, multiplying forms, called schizonts, or into gametocytes, the sexual stages of the parasite. In the present work we studied the differentiation into asexual parasites or gametocytes of the progeny of single, isolated schizonts of the clone 3D7A of Plasinodium falciparum, using monoclonal antibodies specific for the sexual or asexual stages of the parasite. We observed that schizonts obtained from a continuous culture undergoing serial cycles of growth and dilution with fresh red blood cells produced either only gametocytes or only asexual parasites, showing a high degree of commitment to one or the other developmental pathway.

The relative proportion of schizonts which produced gametocytes was very low at low parasite densities in culture, while at high parasite densities a much greater proportion of schizonts produced gametocytes. Nevertheless, at both low and high parasite densities individual schizonts were almost always fully committed to producing only gametocytes or only asexual parasites.
Population genetics of Trypanosoma brucei and the epidemiology of human sleeping sickness in the Lambwe Valley, Kenya
Authors: Mihok S. , Otieno L. H. , Darji N.
Published: June 2009

Numerical taxonomy was used to review isoenzyme variation in isolates of Trypanosoma brucei obtained from cattle, tsetse, humans and wildlife from the Lambwe Valley, Kenya. From isoenzyme information alone, it was possible to classify isolates as to source through the use of linear discriminant functions analysis, with an error rate of only 2% in humans, and 14% over all groups. Differentiation was mostly dependent on patterns in the enzymes ASAT, PEPI, and ICD. Parasites from non-human sources, especially tsetse, were characterized by high isoenzyme diversity, and many unique zymodemes. Observed frequencies of genotypes for ICD, ALAT, and ASAT did not agree with expected frequencies based on random mating of a diploid organism. Deviations were particularly large for tsetse isolates, and were mostly due to a deficiency of one homozygote. Cluster analysis revealed complex relationships among isolates, with patterns evolving through time. Major human zymodemes from the 1970s clustered together with most wildlife isolates from East Africa. This chronic human-wildlife transmission cycle was characterized by ASAT pattern I. Other, minor human zymodemes were associated with a human-cattle transmission cycle characterized by ASAT pattern VII. These original chronic transmission cycles appeared to change in 1980 with the appearance of two new zymodemes in humans. These zymodemes involved changes in ALAT and/or PGM to patterns typical of tsetse and cattle isolates. A resultant epidemic was halted with repeated aerial spraying of endosulfan in 1981. Since then, a variety of new zymodemes of unknown human infectivity have appeared. The origins of these changes are discussed in terms of genetic exchange in tsetse, adaptation to human and cattle transmission cycles, and selection resulting from chronic use of insecticides.
Antibody is responsible for the passive transfer of immunity to mice from rabbits, rats or mice vaccinated with attenuatedSchistosoma japonicumcercariae
Authors: Moloney N. A. , Webbe G.
Published: June 2009

Sera from rabbits, rats and mice multiply-vaccinated with attenuated cercariae ofSchistosoma japonicumconferred high levels of resistance against challenge to naive recipient mice (up to 97, 64 and 60% respectively). Vaccinated rabbit and rat sera were given before challenge and vaccinated mouse serum 5 days after challenge. To show that the protective factors in these sera were antibodies, vaccinated rabbit and mouse sera were fractionated by protein A-Sepharose and the fractions precipitated by 50% ammonium sulphate. The protein A-Sepharose binding or non-binding fractions in vaccinated rabbit serum transferred approximately equal levels of significant resistance to mice, suggesting that both the IgG and non-IgG components of vaccinated rabbit serum are protective. The major part of the protective activity in vaccinated mouse serum was transferred to recipients by the protein A-Sepharose binding fraction, i.e. the IgG antibodies. Heat inactivation of sera at 56 °C for 3 h affected the protective capacity of vaccinated rat sera, but not that of vaccinated rabbit or mouse sera.
Occurrence of entomopathogenic nematodes (Rhabditida: Steinernematidae and Heterorhabditidae) in British soils
Authors: Homininck W. M. , Briscoe B. R.
Published: June 2009

Soil from 403 hedgerow, roadside verge, woodland, heathland or field sites was assessed for presence of entomopathogenic rhabditid nematodes with aGalleria larva baiting technique. Steinernematids were recovered from 48 % of the sites but only one site yielded Heterorhabditis sp. The species recovered most frequently was Steinernema bibionis (Bovien). Another unidentified Steinernema sp. was also isolated. Prevalence of steinernematids in the different types of habitat formed continuum so that roadside verges harboured them most often while heathland sites yielded them least often. Mean soil temperatures at 5 cm were about 15 °C in fields and verges, 13 °C in hedgerows and heathland and 12 °C in woodland. Prevalence of the nematodes varied in different parts of Britain and was influenced by soil type. They were associated with calcareous soils, especially those with a calcareous subsoil horizon. Soils which are periodically or seasonally water-logged were suitable. Soils enriched by humus and hence high in organic matter frequently harboured the nematodes and some suitable soils had significant clay contents or subsoils high in clay. It appears that the two steinernematids are relatively unspecialized species, occurring in diverse habitats and soil types and are adapted to cooler temperatures.
Coproantigen detection for immunodiagnosis of echinococcosis and taeniasis in dogs and humans
Authors: Allan J. C. , Craig P. S. , Garcia Noval J. , Mencos F. , Liu D. , Wang Y. , Wen H. , Zhou P. , Stringer R. , Rogan M. , Zeyhle E.
Published: June 2009

Three ELISA assays, based on hyperimmune rabbit serum raised against adult cestode somatic antigen, were applied in this study for the detection ofTaenia- andEchinococcus-specific antigens in host faeces. The first assay, using an antiserum againstTaenia pisiformisantigen extract, was used in a time-course ofT. pisiformisexperimental infection in dogs. The assay was shown to be considerably more sensitive than microscopical detection of eggs in faeces. Antigen was present in faeces before patency and antigen levels were independent ofT. pisiformisegg output. The second assay, involving a test for human taeniasis based on antibodies againstT. solium, was applied in two field studies carried out in China and Guatemala. The test was highly specific, no false positive reactions occurred with human faecal samples and the test was capable of diagnosing individuals who would not have been detected by coproscopy or treatment to recover the tapeworm. A third assay was designed forE. granulosusand demonstrated 87·5% sensitivity and 96·5% specificity with samples from naturally and experimentally infected dogs withEchinococcusorTaeniainfections. In both the humanTaeniaand canineEchinococcusstudies antigen could be detected in faecal samples from infected hosts stored in 5% formalin for 6 months. Further refinements to these tests for field application are discussed.
Evaluation of a monoclonal antibody-based competition ELISA for the diagnosis of human hydatidosis
Authors: Liu D. , Lightowlers M. W. , Rickard M. D.
Published: June 2009

An antibody competition enzyme-linked immunosorbent assay (ELISA) using 4 different monoclonal antibodies (MAb) raised against major antigens (Antigen 5 and Antigen B) of Echinococcus granulosus was evaluated for the diagnosis of human hydatidosis. The competition assay, using anti-Ag5 MAb 24.14, detected specific antibodies in 70% (131/188) of sera from patients with surgically confirmed E. granulosus infection and 38·5% (10/26) of sera from patients with E. multilocularis infection. None of the sera from patients with Taenia solium cysticercosis (10), T. saginata (2), filariasis (22), strongyloidiasis (19), fascioliasis (4), bilharziasis (4) and amoebiasis (2) tested were positive using a cut-off point established through reaction between MAb 24.14 and normal human sera. The combined use of the MAb 24.14-based competition ELISA with the conventional antibody-binding assay provides a highly sensitive (92·8%) and specific screening system for human hydatid disease diagnosis.
Radiorespirometric detection of macrofilaricidal activityin vitro
Authors: Comley J. C. W. , Rees M. J.
Published: June 2009

Anin vitromethod for studying radiorespiration has been adapted to single macrofilariae. Using this method viable (but not heat-killed)Dipetalonema viteaeandOnchocera gibsonimacrofilariae evolved measurable amounts of14CO2from L-[U-14C]glutamine. Nonlinear and less uniform rates of14CO2evolution were demonstrated with D-[U-14C]glucose, [1-14C]acetate and [1-14C]octanoate. These findings led us to develop anin vitroscreen in which inhibition of14CO2evolution from L-[U-14C]glutamine was used as a parameter for gauging macrofilaricidal activity. Using this screen we have examined the activity of 17 ‘so-called’ antifilarial standards and found a greater degree of sensitivity than shown by other biochemical criteria. Other data obtained suggest a role for radiorespirometry in determining the viability of fragments ofOnchocerca tissue.
Fluctuations in rat liver alanine-amino-transferase activity during experimental nippostrongylosis
Authors: Robertson Lucy J.
Published: June 2009

The activity of the gluconeogenic enzyme, alanine-amino-transferase (ALT), in a preparation from the liver of rats was studied by means of anin vitroassay throughout the course of a primary infection ofNippostrongylus brasiliensis, established by a subcutaneous injection of approximately 4000 3rd-stage larvae. The activity was measured on days 1–14 p.i. in both uninfected and infected rats and a marked pattern in the enzyme's activity was observed. In infected rats, the activity increased from 1·46±0·19 U/g liver on day 1 p.i. to a peak on day 4 p.i. of 10·75±1·62 U/g liver, then decreased to a trough of 0·44±0·18 U/g liver on day 10 p.i. before returning to original levels by day 14 p.i., by which time the infection had been largely eliminated. In uninfected rats the activity of the liver enzyme remained constant throughout this period with a value of 2·54±0·12 U/g liver. The activity of the enzymein vitrowas found to be related to the size of the inoculum on days 4 and 10 p.i. It was proposed that these observations could be due to either (1) a direct effect of the parasite, or (2) a consequence of the host immune response to the infection. In order to investigate the second proposition more fully, liver ALT activity was investigated byin vitroassay on selected days p.i. in rats experiencing a secondaryN. brasiliensisinfection. In these rats the liver ALT activity was observed to reach a peak on day 2 p.i., with an activity of 3·87 ± 0-28 U/g liver, and a trough on day 4 p.i. with an activity of 0·11 ±0·03 U/g liver, returning to similar levels to those measured in uninfected rats by day 7 p.i. When serum prepared from rats having secondaryN. brasiliensisinfections collected on day 4 p.i. was added to the assay, a reduction in the activity of liver ALT activity from both the infected and uninfected rats was measured byin vitroassay. The results are discussed in relation to protein metabolism and gluconeogenesis in rats infected withN. brasiliensis, and also in relation to the host’s immune response to the parasitic infection.
Giardiainfection in pigs: detection andin vitroisolation of trophozoites of theGiardia intestinalisgroup
Authors: Koudela B. , Nohýnková E. , Vítovec J. , Pakandl M. , Kulda J.
Published: June 2009

Giardiainfections were detected in 14 out of 32 weaned, 1 to 2-month-old pigs, used in experiments with coccidia.Giardiatrophozoites were present in the small intestine from the duodenum to the ileum with maximum numbers in the cranial part of the upper jejunum. They were localized mainly on the surface of intestinal crypts. No histological changes accompanied the infection and the infected animals were asymptomatic.Giardiatrophozoites obtained from the intestines of necropsied pigs were isolated in axenic culture in a bile-supplemented TYI-S-33 medium. Morphological features of the trophozoites revealed by both light and scanning electron microscopy proved that the organism belongs to theGiardia intestinalisgroup.
The enigmatic presence of all gluconeogenic enzymes inSchistosoma mansoniadults
Authors: Tielens A. G. M. , Van Der Meer P. , Van Den Heuvel J. M. , Van Den Bergh S. G.
Published: June 2009

The activities of glucose-6-phosphatase (G6Pase), frucrose-1,6-bisphosphatase (FBPase), phosphoenolpyruvate carboxykinase (PEPCK) and pyruvate carboxylase (PC) were determined in homogenates of adultSchistosoma mansoniworms and compared with the activities in homogenates of rat liver and rat skeletal muscle, tissues with a high and a low gluconeogenic capacity, respectively. All four gluconeogenic enzymes were present inS. mansoni. The enzymes were less active than in rat liver, but the activities of G6Pase, PEPCK and PC were at least an order of magnitude higher than in rat skeletal muscle whereas FBPase was approximately equally active inS. mansoniand in rat muscle. Experiments with14C-labelled substrates or [14C]NaHCO3failed to demonstrate the actual occurrence of gluconeogenesis inS. mansoni. Some possible other functions of the gluconeogenic enzymes were investigated. Experiments with inhibitors of PEPCK gave no indications that this enzyme was involved in the degradation of glucose. This was confirmed by13C-NMR experiments which indicated that lactate was formed from phosphoenolpyruvate via the actions of pyruvate kinase and lactate dehydrogenase, and that PEPCK did not participate in the formation of lactate. Substrate cycling between fructose-6-phosphate and fructose-1,6-bisphosphate was demonstrated to occur in adultS. mansoni. This shows that FBPase participates in the glucose metabolism of this parasite.
Opisthorchis viverrini: relationships between egg counts, worms recovered and antibody levels within an endemic community in Northeast Thailand
Authors: Elkins D. B. , Sithithaworn P. , Haswell-Elkins M. , Kaewkes S. , Awacharagan P. , Wongratanacheewin S.
Published: June 2009

Three techniques for estimating the intensity of Opisthorchis viverrini infection in individuals from a Northeast That community are compared. Egg counts were determined using a quantitative formalin/ethyl acetate technique, worm burdens were estimated by expulsion chemotherapy and antibody levels were measured by ELISA. Log-transformed worm and egg counts were closely correlated (r = 0·80), suggesting that both measurements provide good assessments of relative intensity of infection. However, no Opisthorchis worms were recovered from 34 people with high egg counts; probably due to problems with the expulsion technique in some individuals. Examination of egg production per fluke indicated that each fluke contributed an average of 180 eggs per gram (epg) of faeces and fecundity was negatively associated with total worm burden. Serum IgG levels correlated significantly with Opisthorchis egg count (r = 0·61) at two independent assessments. Although significant associations were observed between antibody levels and echinostome infection, analysis suggested that these reflected independent associations between these two variables and Opisthorchis infection and age. We conclude that all three measurements are useful for epidemiological studies.
Studies on the invasion ofNotocotylus attenuates(Notocotylidae: Digenea) into its snail host,Lymnaea peregra. In vitroobservations on the hatching mechanism of the egg
Authors: Murrills R. J. , Reader T. A. J. , Southgate V. R.
Published: June 2009

Media are described which stimulate the eggs ofNotocotylus attenuatusto hatchin vitro. Hatching involves opening of the operculum and emergence of the opercular cord to form a tube measuring approximately 75 μm in length along which the sporocyst passes. The sporocyst is then released from the end of the tube. It is suggested thatin vivothe opercular cord serves to inject the sporocyst through the snail host's gut wall into the haemocoel.
The uptake and incorporation of nucleosides into normal erythrocytes and erythrocytes containingPlasmodium berghei
Authors: Neame K. D. , Brownbill P. A. , Homewood C. A.
Published: June 2009

Normal mouse erythrocytes and erythrocytes containingPlasmodium bergheiwere incubated for 1 h in a medium containing either adenosine, guanosine, cytidine or thymidine labelled with14C or3H. The purine nucleosides, adenosine and guanosine, but not the pyrimidine nucleosides, cytidine and thymidine, were incorporated into the nucleic acid of the parasite–host cell complex. The concentration achieved by all four nucleosides in both normal and parasitized cells was at least as high as that in the suspending medium, showing that not only purines but also pyrimidines enter the parasitized erythrocyte.
Host—parasite relationships ofBlastocrithidia familiarisinLygaeus pandurusScop. (Hemiptera: Lygaeidae)
Authors: Tieszen K. L. , Molyneux D. H. , Abdel-Hafez S. K.
Published: June 2009

Blastocrithidia familiariswere found to be parasitic in the midgut, ileum and rectum ofLygaeus pandurus. The host—parasite relationship is described. Attachment of parasites in the midgut and ileum occurs by interdigitation of expanded flagella over and between the microvilli. No attachment to microvilli was observed where extracellular membranes form well-organized layers which lie parallel to the gut wall and completely separate the microvilli border from the lumen. The extracellular membranes originate from delamination of the outer unit membrane of microvilli which consists of a double plasma membrane. The function of the extracellular membrane layers and their possible role as a peritrophic membrane in preventing parasite attachment is discussed in relation to previous studies on midgut cells in Hemiptera with a similar apical coat on midgut microvilli. In the rectum, parasites attach to the cuticle of the gland cells and not to the rest of the rectal wall. Attachment to the cuticle occurs by the formation of hemidesmosomes. A comparison of the relationship ofB. familiarisand its host to previous ultrastructural studies of associations between kinetoplastid flagellates and their respective hosts is discussed.
Three dimensional structure of the leishmania amastigote as revealed by computer-aided reconstruction from serial sections
Authors: Coombs G. H. , Tetley L. , Moss V. A. , Vickerman K.
Published: June 2009

Computer-aided reconstruction from serial sections has been used to analyse the 3-dimensional structure of entire amastigotes of Leishmania mexicana mexicana and to determine the number, arrangement and volume of each organelle. In two reconstructions, the lysosome-like ‘megasomes’ were the most numerous organelle, there being 34 in one amastigote, and they comprised as much as 15% of the total cell volume. In contrast, as few as 9 glycosomes were present, accounting for less than 1% of the cell volume. The unitary nature of the mitochondrion was confirmed and its complex basket-like structure was revealed. The spatial arrangement of the cell organelles is here displayed in stereo-pairs.
The use of DNA hybridization and numerical taxonomy in determining relationships between Trypanosoma brucei stocks and subspecies
Authors: Paindavoine P. , Pays E. , Laurent M. , Geltmeyer Y. , Le Ray D. , Mehlitz D. , Steinert M.
Published: June 2009

The nuclear DNAs of 71 trypanosome stocks from different African countries, representative of the three Trypanosoma brucei subspecies, and one T. evansi stock, have been analysed by the combined use of restriction endonuclease digestion, gel electrophoresis and molecular hybridization with both trypanosome surface-antigen-specific and undefined genomic DNA probes. In contrast with T. brucei brucei and T. brucei rhodesiense stocks, all the T. b. gambiense stocks are characterized by a conserved, specific DNA band pattern, regardless of the probe. This allows T. b. gambiense to be non-ambiguously identified. On the contrary, T. b. brucei and T. b. rhodesiense, which could not be discriminated by the same criteria, both yield highly variable DNA band patterns. Our data confirm that domestic animals like pig, dog and sheep constitute a potential reservoir for T. b. gambiense. Using a numerical analysis of the DNA hybridization patterns we have measured the degree of similarity between the 72 trypanosome stocks. This investigation shows that all T. b. gambiense stocks are included in the same homogeneous population, while the stocks from the two other subspecies seem to be distributed in several heterogeneous groups, some of these showing correlation with the geographical origin of the trypanosomes. It is concluded that (i) T. b. gambiense stands out as a real subspecies that has undergone a distinct evolution relative to the ‘non-gambiense’ group, (ii) the alleged T. b. rhodesiense subspecies does not fit with any of the groups evidenced by our cladistic analysis and hence does not appear as a distinct subspecies and (iii) ‘non-gambiense’ trypanosomes are probably evolving much more rapidly than T. b. gambiense. Different aspects of trypanosome relationships and evolution are discussed.
Echinococcus granulosus: absorption of cycloleucine and α-aminoisobutyric acid by protoscoleces
Authors: Jeffs S. A. , Arme C.
Published: June 2009

Protoscoleces ofEchinococcus granulosusabsorb the amino acids cycloleucine and α-aminoisobutyric acid (AIB) by a combination of mediated uptake and diffusion. After correcting for the latter, values forKtandVmaxof 0·124 mM and 0·947 nmoles/mg protein/2 min for cycloleucine were calculated; corresponding values for AIB were 0·039 mM and 0·139 nmoles/mg protein/2 min. Both amino acids were accumulated against a concentration gradient and a comparison ofKtandKtvalues determined in mutual inhibition experiments suggested that both cycloleucine and AIB share a common uptake locus (loci). Cycloleucine uptake was pH-dependent and could be inhibited by a variety of other amino acids. Neither D- nor L-proline inhibited cycloleucine absorption but D-methionine, D-alanine, D-leucine, D-valine and D-serine were much more effective inhibitors than their L-counterparts.
Plasmodium falciparum: isolation of intact and erythrocyte-free trophozoites from sorbitol lysates
Authors: Hoppe H. C. , Coetzee J. , Louw A. I.
Published: June 2009

Anin vitroculture ofPlasmodium falciparum(isolate FCUP-1/RSA) was arrested in the trophozoite stage with α-difluoromethylornithine (DFMO), followed by sorbitol treatment to liberate intracellular parasites from infected erythrocytes. Most of the unlysed erythrocytes and ghost membranes were removed by filtration, after agglutination with anti-erythrocyte monoclonal antibodies or wheat-germ agglutinin. A highly purified parasite preparation was obtained after chromatography on an immuno-affinity column consisting of polystyrene particles to which anti-erythrocyte monoclonal antibodies had been adsorbed. Isolated parasites were free of surrounding erythrocyte membranes and structurally intact as assessed by transmission electron microscopy, SDS–PAGE and ELISA.
Preliminary characterization of the lipid and protein components of the protective surface membranes of a pentastomidPorocephalus crotali
Authors: Jones D. A. C. , Henderson R. J. , Riley J.
Published: June 2009

All instars of the pentastomidPorocephalus crotali, in the tissues of rat intermediate hosts and the lung of rattlesnake definitive hosts, are covered by a vesicular or stacked membranous secretory product which is synthesized in sub-parietal cells (SPC) and channelled to the cuticle via multitudinous chitin-lined ducts. In rats this enveloping foam of vesicles survives for the duration of a cuticle. We have purified and partially characterized the lipid and protein composition of lamellate droplets from SPC of infective nymphs. Lipids in the droplets comprised a mixture of neutral and polar lipid classes with cholesterol being the major neutral lipid and phosphatidylcholine the dominant polar lipid. In addition, Triton X-114 phase separation of the protein component of droplets partitioned these into an aqueous phase (with a major band at 60 kDa), a detergent phase with two hydrophobic polypeptides (24 and 16 kDa) and an insoluble pellet containing several minor proteins and major bands at 31 and 107 kDa. Western blotting, with rabbit anti-lamellate droplet antiserum, strongly label only the 60 kDa and the two hydrophobic proteins. Significantly no proteins at all label with serum from infected rats from 50–150 days post-infection, a finding endorsed by indirect fluorescent antibody tests on sectioned V–VII stage nymphs. Possible immunomodulatory functions of SPC-derived surface membranes are discussed and, in this regard, they are compared with pulmonary surfactant, a product of alveolar Type II cells which lines all vertebrate lungs.
On the distribution of a fluorescent ivermectin probe (4″ 5,7 dimethyl-bodipy proprionylivermectin) in Ascaris membranes
Authors: Martin R. J. , Kusel J. R.
Published: June 2009

The distribution of the fluorescent ivermectin derivative (4″ 5,7 dimethyl bodipy proprionylivermectin, referred to here as bodipy ivermectin) was studied in muscle vesicle membranes from the parasite Ascaris suum. Incubation in bodipy ivermectin, at concentrations greater than 1 ng/ml, produced a dose-dependent fluorescence in the vesicles. The level of fluorescence was not depressed (but increased) by prior incubation with 1 μM unlabelled ivermectin. This observation suggested that most of the bodipy ivermectin was free in the lipid phase of the membrane and not associated with a receptor. The trypan blue quenching technique showed that the bodipy ivermectin did not cross the membrane bilayer but remained in the outer monolayer. Lateral mobility of the probe in the membrane was studied using the fluorescence recovery after photobleaching (FRAP) technique. The lateral diffusion coefficient (DL) was 14.0 x 10−10 cm2/s which was nearly three times faster than the lipid probe octadecanoyl-aminofluorescein in membranes from the same preparations; only 46% of the probe was mobile, showing that within a 1.2 μm radius the distribution of the bodipy ivermectin in the membrane was not homogeneous. These observations are used to suggest that: the site of action of livermectin is located in the outer monolayer of the membrane (possibly on the Cl− channel); and that the speed of onset of action in isolated membrane preparations may be limited by diffusion in the membrane.
Cloning and functional expression of a Shaker-related voltage-gated potassium channel gene from Schistosoma mansoni (Trematoda: Digenea)
Authors: Kim E. , Day T. A. , Bennett J. L. , Pax R. A.
Published: June 2009

We have isolated a cDNA (SKvl. 1) encoding a Shaker-related K+ channel from an adult cDNA library of the human parasitic trematode Schistosoma mansoni. The deduced amino acid sequence (512 aa, 56·5 kDa) contains 6 putative membrane-spanning domains (S1–S6) and a pore-forming domain (H5). SKv1.1 is grouped in the Shaker family, but forms a unique branch within this family, on the basis of dendrogram analysis. SKv1.1 shows significant sequence identity with most other Shaker channels, with 64—74% identity in the core region (S1–S6). It has the highest sequence identity with the K+ channel (Ak01a) from Aplysia. Northern blot analysis detected a single primary transcript of 2·8 kb. Southern blot analysis indicated that SKv1.1 is present as a single copy in the genomic DNA of S. mansoni. Expression of SKv1. 1 in Xenopus oocytes produced a rapidly activating and inactivating outward K+ current which is highly sensitive to 4-aminopyridine, but is insensitive to tetraethylammonium, mast cell degranulating peptide, dendrotoxin and charybdo-toxin. The presence of a Shaker homologue in Schistosoma suggests that Sh subfamilies may exist in other lower invertebrates as well as platyhelminths.
Acetyicholinesterase secretion–a parameter for the interpretation of in vitro anthelmintic screens
Authors: Rapson E. B. , Chilwan A. S. , Jenkins D. C.
Published: June 2009

Interpretation of anthelmintic activity using in vitro screens has, until now, relied on the detection of drug-induced effects on nematode development, viability and motility. A novel biochemical parameter dependent upon the spectrophotometric assay of acetyicholinesterase (AChE), an enzyme secreted in large quantities by certain trichostrongylid nematodes, has been developed to replace these often subjective indices of activity. Using Nippostrongylus brasiliensis, a worm frequently employed for primary screening, the secretion of this enzyme in the presence or absence of a large number of drugs in vitro was determined. During a 4-day incubation period in a complex undefined medium without serum, AChE was secreted by normal 4th larval and immature adult stages of the worm in a linear fashion. All modern broad-spectrum veterinary anthelmintics, regardless of their mode of action, dramatically reduced the amount of enzyme secreted. Correlation between the biochemical and observa tional parameters was excellent and the selectivity of the assay when based solely on enzyme secretion was not lost. Other advantages were that the time required for the activity of certain slow-acting compounds to be detected was reduced from 7 to 4 days and that close microscopical examination of the worms was not necessary.
The development and mortality of the non-infective free-living stages of Ostertagia ostertagi in the field and in laboratory culture
Authors: Smith G. , Grenfell B. T. , Anderson R. M.
Published: June 2009

A deterministic model of the population biology of the non-infective free-living phase of Ostertagia ostertagi is described and tested. A comparison of field and laboratory studies indicates that the pre-infective larvae of O. ostertagi spend about twice as long in this phase in the field as in laboratory culture (13 days and 7 days respectively at 15 °C), and that the subsequent transition (i.e. second moult) to the infective phase also proceeds at a much slower rate (about 10 times less at 15 °C) in the field. Because of this discrepancy, estimates of model parameters are based entirely on measurements from field studies. A two-parameter model of pre-infective development in the field is derived. It describes egg and larval development as a direct non-linear function of air temperature. We also show that the mortality of the eggs and pre.infective larvae increases with temperature (although this relationship probably also subsumes a dependence on faecal moisture content). The model is shown to be a good mimic of the population dynamics of the non-infective free-living phase when tested against an independent data set, and is the basis of a larger model of the epidemiology of ostertagiasis.
Characterization of the lipid content ofToxoplasma gondiirhoptries
Authors: Foussard F. , Leriche M. A. , Dubremetz J. F.
Published: June 2009

Quantitative and qualitative analysis of lipids has been performed on a rhoptry fraction purified fromToxoplasma gondiitachyzoites. The lipid to protein ratio was estimated to be 0·26. The cholesterol to phospholipid ratio was unusually high at 1·48. Phosphatidylcholine was the major phospholipid; phosphatidylserine, phosphatidylinositol and sphingomyelin were absent whereas significant amounts of phosphatidic acid and lysophospholipids were found. This pelicular composition could be related to functional involvement of the organelle in host-cell invasion.
Host specificity of and cross-immunity between two strains ofHeligmosomoides polygyrus
Authors: Quinnell R.J. , Behnke J. M. , Keymer A. E.
Published: June 2009

The infectivity of wild and laboratory strains ofHeligmosomoides polygyrus(Nematospiroides dubius) in laboratory mice and in three species of wild British rodent was compared. Wild strains, of the subspeciesH. p. polygyrus, were isolated from wild caughtApodemus sylvaticus. Only very low-level infections of the wild strains became established in laboratory mice. Similar worm burdens of the laboratory strain became established in laboratory mice andA. sylvaticus, although infections inA. sylvaticuswere more short lived. Cortisone treatment of hosts increased the establishment and survival of the heterologous worm strain to that of the homologous strain. In contrast, neither strain of parasite established inClethrionomys glareolusorMicrotus agrestis, and cortisone treatment ofC. glareolusdid not increase establishment. Infection of laboratory mice with the wild-strain parasite induced significant immunity to a challenge infection with the laboratory strain.
Oxantel-activated single channel currents in the muscle membrane ofAscaris suum
Authors: Dale V. M. E. , Martin R. J.
Published: June 2009

The patch clamp technique was used to investigate the action of the anthelmintic drug, oxantel, on nicotinic acetylcholine receptor (nAChR) currents recorded from vesicles of the somatic muscle cells of the nematode parasiteAscaris suum. The amplitudes of the currents were analysed at different membrane potentials to determine the single channel conductance. Also the open and closed durations were measured to determine the kinetic properties of the activated channel. Oxantel activated single nAChR currents throughout a concentration range 10–100 μM, these currents were not observed with oxantel-free pipette solutions. The mean open time of the activated channels at a membrane potential of –75 mV and a concentration of 10 μM was 1·34 ms. At higher concentrations the open times were shorter and voltage sensitive, decreasing in duration on hyperpolarization, thus suggesting open channel block. The kinetics were analysed using a simple channel block model. The forward block rate,K + B, increased with increasing oxantel concentration but showed little increase as the membrane was hyperpolarized.K + Bwas 2·41×107M−1s−1– 50 mV and 2·64 × 107M−1s−1at – 100mV. The unblocking rate constant,K – B, did exhibit voltage sensitivity being 443·6 s−1at – 50 mV and 86·8 s−1at –100 mV. Thus the blocking dissociation constantKB (= K – B/K + B)was 18·5 μM at –50 mV and 3·3 μM at –100 mV. The simple channel block scheme was found to be insufficient to explain fully the observations made; reasons for this are discussed.