bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of the nematicide oxamyl on lipid utilization and infectivity inGlobodera rostochiensis
Authors: Wright D. J. , Roberts I. T. J. , Evans S. G.
Published: June 2009

At field rates (ca 0·1–10 μg active ingredient/ml), non-fumigant nematicides such as oxamyl do not kill plant-parasitic nematodes directly but act by impairing neuromuscular activity. The present study has shown that neutral lipid levels in 2nd-stage (infective) juveniles ofGlobodera rostochiensis, which had been incubated with the oximecarbamate nematicide oxamyl (1 μg a.i./ml) for between 8 and 35 days, were significantly (P< 0·05) greater when compared with controls maintained in water alone. The difference between treatments was found to be due principally to changes in the lipid content in the posterior half of the body which appears to act as the major long-term lipid store. When nematodes were allowed to recover for 72 h following incubation for 35 days with oxamyl, their infectivity was not significantly (P> 0·05) different from that of controls. This work is discussed in relation to the action of oxamyl and similar nematicides and to the use of controlled-release formulations as a means of increasing their efficacy.
Ultrastructural changes associated with exsheathment of infective juveniles ofHaemonchus contortus
Authors: Wharton D. A.
Published: June 2009

Ultrastructural changes associated with exsheathment of the infective juveniles ofHaemonchus contortusare described. Hyaline ring formation occurs associated with annulations 10 and 20 and consists of the dissolution of the basal zone and the inner electron-dense layer resulting in the rupture of the sheath. These changes are consistent with the action of a protease-exsheathing enzyme. There is a significant reduction associated with exsheathment in the size of the excretory cells and the number of excretory granules contained within them. No changes in the oesophagus were observed associated with exsheathment. These, and the observations of earlier workers, suggest that it is the excretory cells and not the oesophagus which are the source of exsheathing fluid during exsheathment.
Can the nematode Capillaria hepatica regulate abundance in wild house mice? Results of enclosure experiments in southeastern Australia
Authors: Barker S. C. , Singleton G. R. , Spratt D. M.
Published: June 2009

The hypothesis that a liver-inhabiting nematode, Capillaria hepatica, can regulate abundance of the house mouse (Mus domesticus) was tested in enclosures, in southeastern Australia. Changes in mouse abundance, and the relationship between mortality and host abundance were compared in three treatment and three control populations. Any effect of C. hepatica on mouse abundance was masked by an unknown regulating factor(s). This factor(s) caused density-dependent mortality in the control and treatment populations and, together with strong seasonal trends in parasite transmission, confounded our test of the ability of C. hepatica to regulate the abundance of house mice. The seasonal trends in transmission have important implications for the potential of this parasite as a biological control agent and for models of the interaction of C. hepatica and mouse populations. Transmission of C. hepatica apparently occurred throughout the 18 month study, further supporting its potential as a biological agent in the control of mouse plagues in this region.
Comparison of isolates and species ofToxocaraandToxascarisby biosynthetic labelling of somatic and ES proteins from infective larvae
Authors: Page A. P. , Richards D. T. , Lewis J. W. , Omar H. M. , Maizels R. M.
Published: June 2009

Infective-stage larvae of three different isolates ofToxocara caniswere intrinsically ([35S]methionine) labelled in culture, to determine the presence of similarities or differences in the somatic and ES antigens expressed between larvae derived from different hosts and different geographical regions. Two other closely related ascaridids,Toxascaris leoninawhich infects cats and dogs, andToxocara vitulorum(Neoascaris vitulorum) which infects cattle, were also compared toT. canislarvae by this method. Overall comparisons were made by 1- and 2-dimensional electrophoresis, while immunological cross-reactivities between the different species were analysed by radio-immunoprecipitation. Our results show that extensive physicochemical characteristics are shared betweenT. canisisolates, both from different hosts and different geographical locations. A substantial overlap was revealed whenT. canisandT. vitulorumantigens were compared, whereasToxascariswas found to produce a distinct antigen profile: this result was independent of whether methionine- or Iodogen-labelled products were being considered. Antigen recognition by polyclonal antibodies raised to all three species and to the cat ascarididToxocara cati, revealed considerable cross-reactivities. The cross-reactions were especially prominent between theToxocaraspecies, a fact further substantiated when reactivity ofT. canisES-specific monoclonal antibodies were tested againstT. leoninaandT. vitulorumantigens. The ES antigens ofT. leoninawere not recognized by theT. canismonoclonals, whereas the majority of these antibodies precipitated antigens ofT. vitulorum. One which did not react withT. vitulorumwas monoclonal antibody Tcn 2, indicating its species-specific reactivity and therefore its potential for the specific diagnosis of human toxocariasis.
Behavioural responses of the cercariae of Cryptocotyle lingua (Digenea: Heterophyidae) to computer-controlled shadow sequences
Authors: Rea J. G. , Irwin S. W. B.
Published: June 2009

The cercariae of Cryptocotyle lingua have a brief but active life during which they do not feed. In order to maximize the probability of infection they must respond to a variety of host-related stimuli yet conserve their finite energy reserves by minimizing unnecessary muscular activity. In laboratory experiments, simulated shadows representing the passage of a fish host were found to increase population activity levels. Evidence was also found for a relationship between shadow duration and the duration of subsequent bursts of swimming activity. Adaptation to continuous shadowing was recorded, its onset and magnitude being dependent on both the frequency and duration of shadows delivered. As cercariae aged they became less responsive to shadow stimuli, especially those of short duration.
Schistosoma mansoni:stage-dependent damage afterin vivotreatment with praziquantel
Authors: Shaw M. K.
Published: June 2009

Thein vivoeffects of a single, subcurative dose (200 mg/kg body wt of mouse) of praziquantel on the structure of the tegument and subtegumental tissues of juvenile (21-, 26- and 30-day-old) and adultSchistosoma mansoniare described. In juvenile worms praziquantel caused only moderate damage to both the tegument and subtegumental tissues although the degree of drug-induced damage was related to both the sex of the worms and to the developmental status of each individual worm. In general, male worms exhibited more extensive and longer lasting surface damage than females. However, the level and extent of the changes increased as the worms became more developmentally advanced with adult worms showing extensive damage to the tegument and vacuolization and disruption of the subtegumental tissues. The possible correlation between the stage-dependent changes in susceptibility to praziquantel and age-related changes, particularly in the phospholipid composition of the outer tegumental membrane is discussed.
A larval paralysis assay for the detection of thiabendazole resistance in trichostrongyles
Authors: Sutherland I. A. , Lee D. L.
Published: June 2009

Infective-stage larvae of trichostrongyle nematodes, either resistant or susceptible to thiabendazole (TBZ), were incubated in eserine, an acetylcholinesterase inhibitor. Paralysis occurred in larvae treated with eserine but significant differences were observed in the percentage of larva immobilized between TBZ-resistant and TBZ-susceptible strains of the nematodes. These differences are probably related to the presence of higher levels of acetylcholinesterase in the TBZ-resistant strains than in the susceptible strains. This could be used as a rapid and inexpensive method of detecting resistance to TBZ in trichostrongyles.
Changes in the messenger RNA population during sporulation of Eimeria maxima
Authors: Ellis J. , Thurlby T.
Published: June 2009

Messenger RNA has been extracted from oocysts of Eimeria maxima. Using the techniques of in vitro translation and SDS–polyacrylamide gel electrophoresis, we have been able to show that major changes in gene transcription occur during sporulation. Following an overall reduction in the abundance of many mRNAs, several genes identified as the result of an increase in the abundance of their transcripts, are highly expressed during the latter stages of sporulation. A study of two genes whose transcription is down-regulated has provided evidence which shows that both single copy and repetitive sequences are regulated during sporulation of the oocyst.
Trichinella spiralis: antigenic epitopes from the stichocytes detected in the hypertrophic nuclei and cytoplasm of the parasitized muscle fibre (nurse cell) of the host
Authors: Lee D. L. , Ko R. C. , Yi X. Y. , Yeung M. H. F.
Published: June 2009

Monoclonal antibodies raised against antigens present in the excretions/secretions (E/S) of larvalTrichinella spiralis, polyclonal antibodies raised against E/S and antisera from rabbits and pigs infected withT. spiraliswere used in conjunction with immunocytochemical techniques to detect antigens in sections of muscle from mice that had been infected withT. spiralisfor 15 or 30 days. The antibodies recognized epitopes in the stichocytes, on the surface of the cuticle, in the lumen of the oesophagus and in the lumen of the intestine of encysted larvae. Monoclonal antibodies 7C2C5and 1H7 and the polyclonal antibodies recognized epitopes in the cavity occupied by the larva, in the cytoplasm of the nurse cell, and in the hypertrophic nuclei of the nurse cell, but did not recognize material in the smaller nuclei of the nurse cell, in the cyst wall or in the surrounding muscle. Monoclonals 3B2E6 and 1D11G8B2, which recognized epitopes in the stichocytes and on the surface of the cuticle of the larvae, gave negative results with the cytoplasm and nuclei of the nurse cell. A polyclonal antibody raised againstTrichuris suisrecognized epitopes in the muscle and hypodermis of encystedT. spiralisbut gave negative results with material in the nurse cell and nurse cell nuclei. The possibility that the antigen detected in the cytoplasm and nuclei of the nurse cell is produced by the stichocytes of the nematode and that it is controlling genes of the altered muscle fibre, either directly or indirectly, is discussed.
Frequency distribution of lymphatic filariasis microfilariae in human populations: population processes and statistical estimation
Authors: Grenfell B. T. , Das P. K. , Rajagopalan P. K. , Bundy D. A. P.
Published: June 2009

This paper uses simple mathematical models and statistical estimation techniques to analyse the frequency distribution of microfilariae (mf) in blood samples from human populations which are endemic for lymphatic filariasis. The theoretical analysis examines the relationship between microfilarial burdens and the prevalence of adult (macrofilarial) worms in the human host population. The main finding is that a large proportion of observed mf-negatives may be ‘true’ zeros, arising from the absence of macrofilarial infections or unmated adult worms, rather than being attributable to the blood sampling process. The corresponding mf distribution should then follow a Poisson mixture, arising from the sampling of mf positives, with an additional proportion of ‘true’ mf-zeros. This hypothesis is supported by analysis of observed Wuchereria bancrofti mf distributions from Southern India, Japan and Fiji, in which zero-truncated Poisson mixtures fit mf-positive counts more effectively than distributions including the observed zeros. The fits of two Poisson mixtures, the negative binomial and the Sichel distribution, are compared. The Sichel provides a slightly better empirical description of the mf density distribution; reasons for this improvement, and a discussion of the relative merits of the two distributions, are presented. The impact on observed mf distributions of increasing blood sampling volume and extraction efficiency are illustrated via a simple model, and directions for future work are identified.
Frequency distribution of Wuchereria bancrofti microfilariae in human populations and its relationships with age and sex
Authors: Das P. K. , Manoharan A. , Srividya A. , Grenfell B. T. , Bundy D. A. P. , Vanamail P.
Published: June 2009

This paper examines the effects of host age and sex on the frequency distribution of Wuchereria bancrofti infections in the human host. Microfilarial counts from a large data base on the epidemiology of bancroftian filariasis in Pondicherry, South India are analysed. Frequency distributions of microfilarial counts divided by age are successfully described by zero-truncated negative binomial distributions, fitted by maximum likelihood. Parameter estimates from the fits indicate a significant trend of decreasing overdispersion with age in the distributions above age 10; this pattern provides indirect evidence for the operation of density-dependent constraints on microfilarial intensity. The analysis also provides estimates of the proportion of mf-positive individuals who are identified as negative due to sampling errors (around 5% of the total negatives). This allows the construction of corrected mf age–prevalence curves, which indicate that the observed prevalence may underestimate the true figures by between 25% and 100%. The age distribution of mf-negative individuals in the population is discussed in terms of current hypotheses about the interaction between disease and infection.
Estimation of relative fecundity inEimeria tenellastrains by a mixed infection method
Authors: Nakamura T. , Konishi T. , Kawaguchi H. , Imose J.
Published: June 2009

The relative fecundity of populations ofEimeria tenellawas estimated by means of mixed infection using electrophoretic variation of glucose-phosphate isomerases (GPIs) as a genetic marker. A decoquinate-resistant strain with GPI-9 isozyme (DR-NIAH), a decoquinate-sensitive one with GPI-1 (DS-Iwate), and three decoquinate-resistant lines (No. 3, 4, and 5) derived from cross-fertilization between DR-NIAH and DS-Iwate, were used. The GPI phenotypes of the No. 3 and No. 4 lines are GPI-9, and that of No. 5 is GPI-1. Mixed infection experiments were performed between DR-NIAH and DS-Iwate, No. 3 and No. 5, and No. 4 and No. 5. DR-NIAH was predominant over DS-Iwate in the mixed infection, whereas, in single infections, the total oocyst output of DR-NIAH was similar to or less than that of DS-Iwate. Among three lines, No. 4 was predominant over No. 5, and No. 5 was predominant over No. 3 in the mixed infection. Relative fecundity between No. 3 and No. 5 and their patterns of oocyst output in single infections were similar to those in the mixed infection. In contrast, No. 5 produced more oocysts than No. 4 in single infections, suggesting that the oocyst production in the mixed infection may be influenced by the mutual interference or competition between the populations ofE. tenellain the chicken caeca.
Studies on a murine model of congenital toxoplasmosis: vertical disease transmission only occurs in BALB/c mice infected for the first time during pregnancy
Authors: Roberts C. W. , Alexander J.
Published: June 2009

The incidence of congenital toxoplasmosis was determined by an ELISA in the litters of BALB/c mice which had been infected 8 weeks before mating, on day 12 of pregnancy, or on both these occasions. Of those mice given the infection for the first time on day 12 of pregnancy, 5 out of 6 gave birth to infected litters with approximately 50% of the individuals in each litter being infected. BALB/c mice which had been infected 8 weeks before mating did not give birth to infected litters, even if they were reinfected on day 12 of pregnancy. Following infection BALB/c mice were found to harbour significantly fewer tissue cysts than the congenic H-2 derivative BALB/K strain. However, chronically infected BALB/K mice also failed to produce infected litters, indicating that tissue cyst burden in the dam did not influence congenital infection at least on the BALB background. This study demonstrates that BALB/c dams chronically infected withToxoplasma gondii, have immunity capable of protecting their embryos from congenital infection, even if the dams are reinfected during pregnancy. Our results demonstrate that the BALB/c mouse can be used as a model of human or ovine congenitalT. gondiiinfection suitable for testing putative vaccines.
Praziquantel: physiological evidence for its site(s) of action in magnesium-paralysedSchistosoma mansoni
Authors: Blair K. L. , Bennett J. L. , Pax R. A.
Published: June 2009

The mechanism whereby praziquantel produces a contraction and subsequent flaccid paralysis (a loss of sensitivity to subsequent stimuli) ofSchistosoma mansoniin a medium containing an elevated Mg2+:Ca2+ratio was investigated. In RPMI, praziquantel produced a concentration-dependent tonic contraction of the parasite with an EC50of 200 nM. Magnesium inhibited the contraction in such a manner as to convert the tonic contraction to a phasic one without altering the peak force generated. The Mg2+-dependent block was non-competitive with praziquantel but was competitive with extracellular Ca2+, ratios of 7·5:1; Mg2+: Ca2+being needed to inhibit the tonic contraction and to induce flaccid paralysis. Flaccid paralysis was associated with a reduced ability of the parasite to take up45Ca2+from the bath compared to parasites that had not entered into flaccid paralysis and flaccid paralysis was reversible. Recovery from flaccid paralysis was accelerated by treatments that are expected to increase Ca2+uptake by the parasite. At a concentration of 500 nM, praziquantel produced 2 distinct phasic contractions in intact parasites incubated in an elevated [Mg2+] medium but only 1 phasic contraction in parasites lacking their surface tegumental membranes. In zero Ca2+I-RPMI, 10 μM praziquantel produced a phasic contraction of intact parasites but did not stimulate contraction of detegumented parasites until Ca2+was reintroduced into the bath. These results indicate that praziquantel interacts with specific Ca2+-permeable sites in the tegumental and sarcoplasmic membranes of the parasite and that under these conditions of elevated Mg2+:Ca2+ratios, these sites become blocked by Mg2+, leading to flaccid paralysis of the parasite.
Experimental population dynamics of Rhabdias bufonis (Nematoda) in toads (Bufo bufo): density-dependence in the primary infection
Authors: Goater C. P.
Published: June 2009

Density-dependence in worm establishment, numbers, biomass and larval production were examined in primary infections of 0, 10, 40, 80 and 160 larvae of the lung nematode, Rhabdias bufonis in the common toad, Bufo bufo. The infection procedure established 4 non-overlapping levels of infection which persisted until 6 weeks post-infection (p.i.), after which there was an overall decline up to 12 weeks p.i. Worm numbers had no direct effect on adult worm survival but temporal changes in worm weight were density-dependent. Adult worm establishment in the lungs declined significantly as the numbers of worms in the lungs increased. At the lowest exposure dose, 86% of the larvae administered reached maturity in the lungs while at the highest, only 37% did so. Also, the numbers of immature larvae outside the lungs increased as adult worm numbers increased. Both features provide evidence for a threshold limit to the numbers of worms maturing in the lungs. Worm numbers also affected larval output per host and per capita fecundity. A significant positive relationship between per capita fecundity and per capita worm weight suggested that density-dependence acted primarily to constrain the growth of individual worms. Finally, the constraints imposed on worm growth and fecundity were apparently relaxed when worm density decreased, providing evidence for density-dependent flexibility in per capita fecundity. Density-dependence in worm establishment and per capita fecundity are mechanisms which may potentially regulate this host–parasite interaction in the field. Both mechanisms may be functionally related to physical space limitations in the lungs, within which worms must compete for finite nutrients.
High frequency of antigenic variation inTrypanosoma brucei rhodesienseinfections
Authors: Turner C. M. R. , Barry J. D.
Published: June 2009

Rates at whichTrypanosoma bruceirhodesiense trypanosomes switch from expression of one variable antigen type (VAT) to that of another have been determined in cloned populations that have been recently tsetse-fly transmitted. Switching rates have been determined between several, specific pairs of VATs in each population. High rates of switching were observed in 2 cloned trypanosome lines, each derived from a separate cyclical transmission of the same parental stock and each expressing a different major VAT. Five estimates of the switching rate between one particular pair of VATs were consistently high (approximately 1 × 103switches/cell/generation). These high switching rates were similar both in bloodstream populations of mice and in populations confined to subcutaneously implanted growth chambers in mice, thus indicating that the interaction of the bloodstream population with other trypanosome populations in the lymphatics or extravascular sites in systemic infections did not influence the estimates of the rate of switching. Fourteen estimates were made of VAT-specific switching rates in bloodstream infections involving 8 combinations from among 6 VATs. Switching rate estimates were VAT-specific and showed considerable variation between different combinations of VATs — from 1.9 × 10−6to 6.9 × 10−3switches/cel/generation. The rates of switching to different metacyclic-VATs were, however, very similar. Summation of between 3 and 5 VAT-specific switching rate values in each of 4 experiments conducted in bloodstream infections has provided minimum estimates of the overall rate of antigenic variation: 2.0−9.3 × 10−3switches/cell/generation. These values are between 20 and 66000-fold higher than previously published estimates. It is likely that at least 1 in every 100 trypanosomes switches its VAT expression every generation.
Theilerial parasites isolated from carrier cattle after immunization withTheileria parvaby the infection and treatment method
Authors: Maritim A. C. , Young A. S. , Lesan A. C. , Ndungu S. G. , Mutugi J. J. , Stagg D. A.
Published: June 2009

Groups of cattle were immunized with 10−2dilutions of sporozoite stabilates ofTheileria parva lawrenceiderived from African buffaloes either alone or in combination withTheileria parva parvaderived from cattle and concomitant treatment with either long or short-acting formulations of oxytetracyline. At 90 or 120 days after infection, uninfectedRhipicephalus appendiculatusnymphal ticks were applied to individual immunized cattle and the resultant adults ticks were applied to individual susceptible cattle. Theilerial infection developed from ticks fed on 6 out of 11 animals investigated for evidence of a carrier state. Two additional animals were shown by cell-culture isolation to have persistent theilerial infections. Nine cattle infected with the parasites from carrier animals were treated with parvaquone and 7 recovered. These recovered cattle were then challenged with the original immunizing stabilates at 10° dilution together with the original immunized and carrier cattle. Six out of 7 cattle which had recovered from carrier-derived infection succumbed to this challenge and died but none of the original immunized cattle showed theilerial reactions. When a carrier-derived sporozoite stabilate was used to challenge cattle immune to the original immunizing parasite, they proved to be immune. Cattle immune to the carrier-derived parasites were all immune to challenge with the original parasite. A monoclonal antibody profile aginstT. parvaschizonts isolated by cell culture from samples of the experimental animals did not appear to be sensitive enough to determine the antigenic differences between the carrier-derived parasite and the original immunizing parasite. Indications are that the carrier state is not likely to produce new antigenic strains which would be dangerous to immunized cattle.
Identification of common surface antigens amongBabesia bigeminaisolates by using monoclonal antibodies
Authors: Figueroa J. V. , Buening G. M. , Kinden D. A. , Green T. J.
Published: June 2009

A group of monoclonal antibodies (MAb) was used to immunochemically characterizeBabesia bigeminasurface components. Two surface reactive MAb by an IFAT test were subsequently shown to bind to epitopes on the external surface of the parasite plasma membrane as evidenced by immunoelectron microscopy. Parasite components with relative sizes of 68, 62, 60, 58, 56, 54, 51, 49, 48, 47, 43, 36 kDa were identified with the group of MAb in at least 6 geographically differentB. bigeminaisolates. The antigenic components were demonstrated to be species-specific and apparently predominant. Both polyclonal antibodies (immune bovine serum) and highly diluted MAb specifically reacted with such bands producing a strong signal in Western blots.
The effect ofPlasmodium falciparumexo-antigens on the morphology of uninfected erythrocytes
Authors: Read D. G. , Bushell G. R. , Kidson C.
Published: June 2009

It was observed that uninfected red cells resuspended in supernatant fromPlasmodium falciparumcultures, then examined between a glass slide and cover-slip, assumed varying morphologies. A series of experiments suggested thatP. falciparumreleases molecules which cause red cells to become stomatocytic (cupped). These molecules, some of which are heat- stable, have an apparent molecular weight < 12 kDa, are released at or about schizogony, and do not bind tightly to erythrocytes.
The serotoninergic, cholinergic and peptidergic components of the nervous system in the monogenean parasite,Diclidophora merlangi: a cytochemical study
Authors: Maule A. G. , Halton D. W. , Johnston C. F. , Shaw C. , Fairweather I.
Published: June 2009

Confocal scanning laser microscopy has been employed with immunocytochemical techniques to map the distribution of serotoninergic and peptidergic components in the nervous system of the monogenean gill-parasite,Diclidophora merlangi; results are compared with the distribution of cholinergic components, following histochemical staining for cholinesterase activity. While all three neurochemical elements are present in the central and peripheral nervous systems, the cholinergic and peptidergic systems dominate the CNS, whereas the PNS has a majority of serotoninergic nerve fibres. The cholinergic and peptidergic neuronal pathways overlap extensively in staining patterns, suggesting possible co-localization of acetylcholine and neuropeptides. Within the peptidergic nervous system, immunoreactivity to the pancreatic polypeptide family of peptides and FMRFamide were the most prevalent.
Regulation of macrophage-mediated larvicidal activity inEchinococcus granulosusandMesocestoides corti(Cestoda) infection in mice
Authors: Jenkins P. , Dixon J. B. , Rakha N. K. , Carter S. D.
Published: June 2009

Killing of metacestodes by normal or post-infection macrophages and the regulation of this activity by cytokines were studied invitro. The protoscolecidal activity of normal macrophages againstEchinococcus granulosuswas inhibited by a product of naive T-enriched lymphocytes co-cultured with protoscoleces (PSC). By contrast, supernates from co-cultures ofMesocestoides cortitetrathyridia (MCT) and T-enriched or B-enriched normal lymphocytes increased killing of MCT by normal macrophages. Larvicidal activity (against both PSC and MCT) was enhanced by high concentrations of macrophage-activating factors produced by Con A-stimulated rat lymphocytes (Con A-LK), but was reduced by low concentrations of these factors.
The sex ratio of Plasmodium gametocytes
Authors: Schall J. J.
Published: June 2009

Sex ratio theory usually predicts an equilibrium sex ratio and equal proportions of males and females in a population, including the progenitors of the reproductive cells of protozoans. This proposal was tested with three species of malarial parasites of lizards, Plasmodium mexicanum of the western fence lizard, and P. agamae and P. giganteum of the African rainbow lizard, using single samples from naturally infected lizards, repeated samples from free-ranging lizards (P. mexicanum only), and repeated samples from laboratory maintained animals. Macrogametocytes were usually more abundant than microgametocytes, and were slightly larger, revealing a typically greater investment of resources by the progenitors of female reproductive cells. However, the proportion of microgametocytes varied among the three species and among infections within each species of Plasmodium. The sex ratio of gametocytes often remained constant within infections followed over time even if the absolute number of gametocytes was changing. However, the equilibrium sex ratio of gametocytes varied among those infections that had an unchanging microgametocyte proportion. Thus, although an equilibrium sex ratio apparently occurs for most infections, there appears to be no characteristic proportion of microgametocytes for any of the species. Potential explanations for this conflict with theory are presented.
Transport processes of 2-deoxy-D-glucose in erythrocytes infected withPlasmodium yoelii, a rodent malaria parasite
Authors: Izumo A. , Tanabe K. , Kato M. , Doi S. , Maekawa K. , Takada S.
Published: June 2009

The transport processes of D-glucose inPlasmodium yoelii-infected mouse erythrocytes were investigated using 2-deoxy-D-glucose (2DOG), a non-metabolizable analogue of D-glucose. Infected cells showed an increase in the uptake of 2DOG compared to uninfected controls, and an effect which was more prominent in cells with mature-stage parasites. Kinetic studies measuring the initial rates of 2DOG uptake revealed two components in infected cells with late trophozoite and schizont-stage parasites: a simple diffusion system and a carrier (transporter)-mediated system. The transporter was common for D-glucose and 2DOG and had a kinetic constant indicating a high affinity for 2DOG (theKm= 0·18 mM and theVmax= 0·61 mmol/1010cells/min), as compared to the constant of the mouse erythrocyte carrier (theKm= 10 mM and theVmax= 1·8 mmol/1010cells/min). Determination of the distribution of [3H]2DOG in infected cells and experiments with metabolic inhibitors indicated that the simple diffusion system localizes in the membrane of host cells and the transporter in the parasite plasma membrane. The parasite glucose transporter was much less sensitive to cytochalasin B than that of the host cells and the uptake of 2DOG via the transporter was dependent on energy. Based on these findings, the following features emerge: D-glucose first gains access to the cytosol of infected erythrocytes via the simple diffusion system, which appears after infection by the parasite, and an active uptake against the concentration gradient takes place at the parasite plasma membrane via the parasite glucose transporter in an energy dependent manner. Finally, an energy transduction mechanism for the transport of glucose across the parasite plasma membrane is discussed.
Density dependence in establishment, growth and worm fecundity in intestinal helminthiasis: the population biology ofTrichuris muris(Nematoda) infection in CBA/Ca mice
Authors: Michael E. , Bundy D. A. P.
Published: June 2009

The results are presented of an experimental study of the population biology of chronicTrichuris muris(Nematoda) infection in cortisone-treated CBA/Ca mice. Attention is focused upon both the validity of the common use of faecal egg counts to demonstrate density dependence in helminth fecundity, and the identification of other possible density-dependent mechanisms that may regulate worm numbers in chronic trichuriasis. The results show that faecal egg counts, although demonstrating high daily variation, are not an artefact of host faecal output but a significant density-dependent function of worm burden. This finding contrasts with the observations onHeligmosomoides polygyrusinfection in outbred MF1 mice, but accords with similar studies in a wide variety of host - helminth systems. Worm establishment in the murine host is found to be a density related function of infection dose. This is attributed to the probable existence of a physical gut-carrying capacity in the murine host forT. muris. Worm distribution in the gut is also shown to be density dependent, with worms being displaced from the caecum to the colon at increasing intensities of infection. The sex ratio of the adult parasites, however, is found to be both unitary and independent of worm burden. Evidence for a significant density-dependent decline in femaleT. murisgrowth or size is presented. The results also show a significant positive association between femaleT. murisweight andper capitafecundity. These findings indicate that the stunted growth of individual worms at high parasite densities may be a potential mechanism underlying density dependence in helminth fecundity.
The eggs and oncomiracidia of Encotyllabe spp. and the relationship between encotyllabines and other capsalid monogeneans
Authors: Whittington I. D. , Kearn G. C.
Published: June 2009

The eggs and oncomiracidia of two species of the capsalid genus Encotyllabe are described. These parasites were identified tentatively as E. caballeroi Velasquez, 1977 and E. caranxi Lebedev, 1967. If these identifications are correct, then E. caballeroi is recorded from two new hosts, Gymnocranius audleyi and the nemipterid Scolopsis monogramma, and E. caranxi from a new host, Pseudocaranx dentex, and a new locality, Heron Island, Queensland, Australia. Encotyllabines have not previously been recorded from fishes of the family Nemipteridae. The eggs of the two parasites failed to hatch spontaneously and did not hatch when exposed to a variety of potential hatching stimuli, but the oncomiracidia within survived for many weeks. Oncomiracidia expelled from eggs by cover-slip pressure are unciliated and possess a saucer-shaped haptor like that of other capsalids with three pairs of median sclerites and 14 marginal hooklets. The paths of tendons associated with the accessory sclerites and the presence of haptoral loculi suggest that encotyllabines are related to the trochopodines. Observations on a single juvenile specimen of E. caballeroi show that the accessory sclerites and the tendons are lost early in development and that one pair of hamuli (probably the posterior pair) ceases to grow early in post-oncomiracidial life. The loculi persist a little longer but also disappear before full sexual maturity is reached.
Dactylogyrus (Monogenea) communities on the gills of roach in three lakes in Central Finland
Authors: Koskivaara M. , Valtonen E. T.
Published: June 2009

Dactylogyrus (Monogenea) species were studied on the gills of roach (Rutilus rutilus) from a total of 293 fish in 3 interconnected lakes in Central Finland. One of the lakes is eutrophic and polluted by a paper and pulp mill, one is eutrophic and one is oligotrophic. Nine Dactylogyrus species were found. The structure of the monogenean communities was analysed at the component and infracommunity level and the Dactylogyrus fauna of the lakes was compared. Although it was found that the component communities tended to be very similar there were also differences. The abundance and diversity were highest in the polluted lake; the infracommunities of this lake were considerably more often dominated by Dactylogyrus micracanthus and the similarities between the infracommunities were higher within the lakes than between the lakes. It is suggested that these differences are due to the differing water quality of the lakes. The nature of the monogenean community, its possible interactivity, is also discussed.
Physiology of obliquely striated muscle fibres withinGrillotia erinaceusmetacestodes (Cestoda: Trypanorhyncha)
Authors: Ward S. M. , Allen J. M. , McKerr G.
Published: June 2009

The tentacular bulb ofGrillotia erinaceusmetacestodes consists of obliquely striated muscle fibres with obvious motor end-plates. In this study isometric tension recordings and intracellular microelectrodes have been used to record mechanical and electrical activity from single isolated bulbs. Bulbs were mechanically quiescent and displayed resting membrane polentials (RMP) in the region of −49 to −64 mV with a mean RMP of −56 mV (n= 60). The membrane potential varied with [K+]oin a manner consistent with the RMP being determined largely by the K+equilibrium potential. High K+solution (> 15 mM) caused membrane depolarization and contraction of the preparation with the contraction showing both phasic and tonic components. L-glutamate caused membrane depolarization, contraction of quiescent preparations and increased the amplitude of electrically evoked responses. In contrast, 5-HT, dopamine, histamine, adrenaline, GABA, noradrenaline and D-glutamate, at concentrations up to and including 10−3M, were without apparent affect, although acetylcholine, at relatively high concentrations (≥ 10−4M) slightly reduced the amplitude of field-evoked contractions.
Quantitative modelling and prediction of development times of the free-living stages of Ostertagia ostertagi under controlled and field conditions
Authors: Young R. R. , Nicholson R. M. , Tweedie R. L. , Schuh H.-J.
Published: June 2009

The development of the free-living stages of Ostertagia ostertagi incubated at constant temperatures from 5 to 27 °C and in dung pats in the field was observed. The death rates were adequately described by a single exponential function and the distribution of times for development by a delayed gamma density function. The times of appearance of selected development stages such as maximum numbers of embryonated eggs and half the maximum number of infective larvae, were highly dependent on temperature. The relationships between these times and temperature were adequately described by the Arrhenius equation. The parameters of this equation and mean hourly temperatures recorded in dung pats in the field were used to predict development times in the field. A comparison of predicted and observed times showed that an initial delay accounted for a large proportion of the time required for development in dung pats, particularly the embryonation of eggs. This delay was attributed to lack of aeration associated with high moisture content of the dung pat.
Action of cyclosporin A on the tapewormsHymenolepis microstoma, H. diminutaandMesocestoides corti in vivo
Authors: Chappell L. H. , Wastling J. M. , Hurd Hilary
Published: June 2009

Thein vivoactivity of two cyclosporins, cyclosporin A (CsA) and a non-immunosuppressive derivative of dihydrocylosporin A (DHCsA-d) against three tapeworms,Hymenolepis microstoma, H. diminutaandMesocestoides corti, has been assessed. CsA reversibly reduced the dry weight ofH. microstomain the mouse, briefly delayed oviposition and had a statistically significant effect on worm numbers recovered. Oral and subcutaneous treatments of both CsA and DHCsA-d were effective in reducing worm weight; juvenile worms were most susceptible but worms of all ages responded to drug by a dramatic reduction in weight from which they recovered. Multiple courses of CsA were no more active than single courses of treatment but dose response suggested that a threshold level of drug was necessary to evoke activity. By contrast,H. diminutain the rat was completely unaffected by CsA but no explanation for the differences in drug response by these two closely related helminths is forthcoming.Mesocestoides cortiresponded reversibly to CsA in the mouse by a reduction in asexual proliferation of both liver and peritoneal cavity tetrathyridia. The data presented argue in favour of a range of anti-parasitic activities by cyclosporins but the details of the various putative modes of action remain to be defined.
Hymenolepis microstoma: a change in susceptibility to resistance with increasing age of the parasite
Authors: Howard R. J.
Published: June 2009

Hymenolepis microstoma from secondary infections in mice were found to grow initially more slowly than H. microstoma from primary infections. Eventually a similar rate of growth was attained by both kinds of worm. After transplantation, young worms (≤4 days old) grew more slowly in previously infected than in naive mice. In contrast, 10-day-old worms grew equally well in naive or resistant mice. The administration of cortisone to mice during a secondary infection of H. microstoma inhibited the stunting of growth in young worms which were able to grow as well as those in a primary infection. The effects of the cortisone persisted for less than 4 days. Worms in a secondary infection given 4days after cortisone treatment were stunted in growth. These experiments suggest that the susceptibility of the worms to the resistance of the mouse applies to the first 4 days within the host. The loss or reduction of this susceptibility might be associated with the worms' entry into the bile duct which occurs 3–4 days after infection.
Naturally occurring immunoglobulin Mantibodies toToxoplasma gondiiin Japanese populations
Authors: Konishi E.
Published: June 2009

Varying degrees of naturally occurring immunoglobulin (Ig) M antibodies toToxoplasma gondiiwere observed in almost all of adult Japanese populations negative for IgG antibodies as determined by an enzyme-linked immunosorbent assay (ELISA). The antibody activity was reduced by absorption of sera withToxoplasmasoluble antigen or by 2-mercapto-ethanol treatment of the IgM fraction after sucrose density gradient centrifugation. Umbilical cord sera had almost no detectable IgM antibodies, and the ELISA value in infants increased with age until 1 year. Most paired sera collected from adults at a 1-year interval showed constant IgM antibody levels, suggesting retention of natural IgM antibodies throughout their lives without changing ELISA values of ≥ 0·1/year. Polar staining was observed in immunofluorescent studies for 14 serum samples with natural IgM antibody levels of ≥ 0·5, while samples obtained from a pregnant woman with natural IgM antibody levels of ≥ 0·9 reacted to the whole organism as was observed in positive sera of acute patients. Western blotting analysis revealed that natural IgM antibodies were directed to multiple antigen molecules. The band pattern differed slightly from one serum to another, but almost consistent patterns were observed in sera sequentially obtained from an adult over 4 years.
Worm burdens, acquired resistance and live weight gains in lambs during prolonged daily infections with Trichostrongylus colubriformis (Giles, 1892) Loos, 1905
Authors: Chiejina S. N. , Sewell M. M. H.
Published: June 2009

Three groups of lambs, aged 3, 5 and 6 months respectively, were infected daily with 5000 infective larvae of Trichostrongylus colubriformis for periods of 15–20 weeks. Some of the lambs also received a single challenge infection at the end of week 16. The course of the infections was monitored by means of faecal egg counts, measurement of live-weight gains and regular post mortem worm counts.

There was an initial rapid increase in egg counts soon after patency, which was followed by an exponential fall in the counts in most lambs. This fall seemed to precede the expulsion of worms by a few weeks and was associated with reduced fecundity in the female worms. Furthermore, although the trend of the egg counts of some lambs suggested that a self-cure reaction had taken place, in a number of these lambs the low faecal egg counts did not reflect the size of their worm burden.

Heavy worm burdens were usually associated with clinical symptoms of trichostrongylosis, including anorexia, diarrhoea and loss of weight. As the lambs developed resistance to reinfection and expelled their worm burden a rapid clinical recovery occurred, except in a few lambs which appeared to have suffered irreversible damage from the earlier heavy worm burden.

The worm burden in most lambs appeared to be cumulative during the first 4–8 weeks before they developed a strong resistance to reinfection. There was considerable loss of the adult worm burden by 8–15 weeks after initial infection and some evidence of stunting in the remaining parasites.

The immunological control of T. colubriformis infections in these lambs was achieved by means of the development of resistance to reinfection, inhibition of the ovulation of the female worms, stunting of adult worms and expulsion of adult worms by resistant lambs. These may be separate immune phenomena requiring different thresholds of parasitic material in individual animals, depending on their age, the rate and duration of infection and their innate ability to develop resistance to the parasite.
Characterization ofTrichomonas vaginalishaemolysis
Authors: Dailey D. C. , Te-Hung C. , Alderete J. F.
Published: June 2009

The haemolytic activity of liveTrichomonas vaginalisorganisms was investigated. Optimal haemolysis of human erythrocytes was observed at a parasite to erythrocyte ratio of 1:5 during a 2 h incubation period. No haemolytic activity was detected in concentrated culture supernatants after overnight growth of trichomonads or when parasites were separated from erythrocytes by a 3 μm filter, suggesting a contact-dependent mechanism for haemolysis. The haemolytic activity was temperature-dependent and maximal haemolysis occurred at 37 °C. Treatment of trichomonads with metronidazole reduced levels of haemolysis by > 50%. Maximal haemolysis occurred at the pH range of the vagina during trichomoniasis.N-μ-tosyl-L-lysyl-chloromethyl ketone and iodoacetamide, inhibitors of trichomonad cysteine proteinases, reduced the haemolytic activity of live parasites.
Monoclonal IgM rheumatoid factor-like anti-globulins enhance the inhibitory effects ofPlasmodium falciparum-specific monoclonal antibodiesin vitro
Authors: Stuart M. K. , Green T. J.
Published: June 2009

Monoclonal IgM rheumatoid factor-like anti-globulins were produced byin vitrostimulation of naive BALB/c spleen cells with lipopolysaccharide, and by hyperimmunization of mice with merozoites ofPlasmodium falciparum, followed by fusion of the spleen cells to mouse myelomas.In vitro, these anti-globulins augmented the inhibitory effects ofP. falciparum-specific polyclonal mouse sera and monoclonal IgG1 and IgG2b antibodies by binding to Fc fragments of IgG molecules attached to blood-stage parasites. In some instances, the presence of anti-globulins correlated with an increase in the number of schizonts which failed to disperse merozoites. In other cases, parasitaemia remained low in the absence of the schizont inhibition phenomenon, suggesting that anti-globulins contribute to host cell protection not only by agglutinating merozoites, but also by increasing the density of the antibody coat surrounding the parasites, thus interfering with parasite receptor-erythrocyte ligand interactions. The anti-globulins were not inhibitory when added to parasite cultures containing IgG not specific for P. falciparum. These results may help explain the function of IgM anti-globulins found at elevated serum levels in some patients with malaria or other chronic infectious diseases.