bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultrastructural changes associated with reversal of chloroquine resistance by verapamil in Plasmodium chabaudi
Authors: Ohsawa K. , Tanabe K. , Kimata I. , Miki A.
Published: June 2009

Reversal of chloroquine (CQ) resistance by verapamil, a Ca2+ antagonist, has been shown in CQ-resistant human and rodent malaria parasites. Here, we report ultrastructural changes associated with this phenomenon in CQ-resistant Plasmodium chabaudi (AS strain) after infected mice were administered CQ and verapamil. At parasitaemias of 5–7%, CQ at 6 mg/kg caused little morphological effect on CQ-resistant parasites. In contrast, co-administration of CQ and verapamil at 50 mg/kg induced swelling of food vacuoles with clumped pigment at 2.5 h. Morphological changes other than food vacuole enlargement occurred at 21 and 45 h: disappearance of endoplasmic reticulum, formation of myelin structures, focal cytoplasmic vacuolization and coarse clumping of electron-dense material in nuclei. These structural changes appeared to be very similar to those observed in CQ-sensitive P. chabaudi in mice injected with CQ alone or CQ plus verapamil. On the other hand, verapamil at 50 mg/kg alone did not induce any effect on both CQ-sensitive and CQ-resistant P. chabaudi. These results suggest that swelling of the food vacuoles is an initial event associated with reversal of CQ-resistance by verapamil.
Evidence for translational control of β-tubulin synthesis during differentiation ofLeishmania donovani
Authors: Bhaumik M. , Das S. , Adhya S.
Published: June 2009

Tubulin biosynthesis was rapidly induced during transformation of the mammalian (amastigote) stage of the kinetoplastid parasiteLeishmania donovanito flagellated promastigotes. However, transcription of β-tubulin genes occurred constitutively, as judged by nascent RNA synthesis in isolated nuclei and Northern blotting of steady-state mRNA. Two mRNA species of 2.2 and 2.4 kb were shared by the two cell-types, while a third 2.6 kb species, constituting about 20% of the total, was present in large amounts in promastigotes. RNase protection experiments demonstrated sequence micro-heterogeneity in the 5′-untranslated region, the pattern of which was identical in promastigotes and amastigotes. By primer extension assays, heterogeneity in the 5′-terminal cap structure of amastigote β-tubulin mRNA and differential pausing of reverse transcriptase within the mini-exon leader region were detected. These differences correlated with enhanced translational efficiency of tubulin mRNA from promastigotes in a rabbit reticulocyte lysate system. The results indicate that translational control plays a major role in tubulin induction duringL. donovanidifferentiation.
Ultrastructure and microanalyses of the protoscolex hooks ofEchinococcus granulosus
Authors: Smith S. A. , Richards K. S.
Published: June 2009

The rostellar distal cytoplasm ofEchinococcus granulosusprotoscoleces is characterized by extensive basal membrane infoldings, prominent hemidesmosomes and is subtended by a lamina reticularis with microfibrils of approximately 10 nm diameter that occasionally show a 55 nm banding periodicity. The rostellar hooks, in 2 rows, each have a blade, guard and handle region and possess a central amorphous pulp, a middle microfibrillar medulla with microfibrils of approximately 4 nm diameter, and a complex outer cortex in all but the proximal region of the guard and the base of the handle. In these regions additional material, of similar electron density to the medulla, but lacking the fibrillar substructure, occurs and gives the areas a lobed appearance. Energy-dispersive X-ray microanalysis of whole hooks demonstrated the presence of sulphur and trace quantities of phosphorus. X-ray near-edge absorption spectra resembled those of cystine, feather and hair and showed the sulphur to be predominantly in the form of disulphide linkages. X-ray diffraction patterns of whole hook preparations revealed 2 diffuse rings with equatorial spacings of 7·99 Å and 15·22 Å, thus differing from vertebrate keratins.
Characterization of proteolytic enzymes from larval and adult Nippostrongylus brasiliensis
Authors: Healer J. , Ashall F. , Maizels R. M.
Published: June 2009

Proteases from infective larval (L3) and adult stages of Nippostrongylus brasiliensis were investigated with a combination of techniques involving gelatin degradation and cleavage of fluorogenic substrates. Analysis of L3 excretory–secretory (ES) products revealed enzymes of Mr 51, 58, 79, ~ 150 and ~ 250 kDa. Inhibition profiles indicate that the major 51 kDa protease is a metallo-enzyme. Significantly, little activity was present in larval somatic extracts, suggesting the synthesis of zymogens or precursor forms prior to secretion. Adult ES contained a distinct enzyme, of 50 kDa, and a number of other proteases were detected in somatic extracts of this stage, ranging from 51 to > 300 kDa. The largest of these adult somatic enzymes is also a putative metallo-protease. While nearly all enzymes from both L3 and adult are heat labile, incubation at 100 °C generated a previously unobserved activity at 20 kDa. Furthermore, a protease of similar size may be found in uninfected rat intestinal tissue, suggesting specific uptake of a host-associated enzyme by the parasite in the form of an inactive, heat-labile complex.
Synthesis and degradation of glycogen by Schistosoma mansoni worms in vitro
Authors: Tielens A. G. M. , Celik C. , Heuvel J. M. Van Den , Elfring R. H. , Bergh S. G. Van Den
Published: June 2009

The glycogen stores of adult Schistosoma mansoni worms could be labelled by incubation of the worms, after an initial reduction of their glycogen content, in the presence of [6-14C]glucose. Subsequent breakdown of the labelled glycogen by the parasite revealed that glycogen was degraded to lactate and carbon dioxide. The degradation of glycogen, as compared to that of glucose, resulted in slightly different ratios of these two end-products. This indicates that glycogen breakdown did not replace glucose breakdown to the same extent in all cells and that Krebs-cycle activity was not uniformly distributed throughout the cells of this parasite. Both fructose and mannose could replace glucose as an energy source and the rate of glycogen synthesis from either of these two carbohydrates was higher than from glucose. No indications for glyconeogenesis from C3-units were found. Glycogen metabolism of S. mansoni was not influenced by hormones of the mammalian host. It is regulated by the external glucose concentration and by the level of the endogenous glycogen stores. Studies on paired and unpaired worms showed that no interaction between male and female was necessary for the synthesis of glycogen by female worms.
The occurrence of schistosomin, an antagonist of female gonadotropic hormones, is a general phenomenon in haemolymph of schistosome-infected freshwater snails
Authors: De Jong-Brink M. , Elsaadany M. , Soto M. S.
Published: June 2009

In haemolymph ofLymnaea stagnalis, parasitized with the digenetic trematode parasiteTrichobilharzia ocellata, a neuropeptide (schistosomin) occurs which antagonizes female gonadotropic hormones, e.g. calfluxin (CaFl). By means of an ultracytochemical hormone-assay, the CaFl assay, it was demonstrated that the occurrence of schistosomin is a general phenomenon in schistosome-infected freshwater snails. Haemolymph of the schistosomiasis-transmitting snail speciesBiomphalaria glabrataandB. pfeifferi, parasitized withSchistosoma mansoni, also appeared to contain an antagonizing factor, i.e. schistosomin. In contrast, in haemolymph ofL. stagnalisparasitized withDiplostomum spathaceum(Diplostomatidae) no schistosomin could be found. This suggests that schistosomin may only occur in snails infected with parasites belonging to the Schistosomatidae. The effect of schistosomin is rather specific. Haemolymph ofB. glabrataparasitized withS. mansonihad not the capacity to inhibit the response to CaFl in the target organs for CaFl, the albumen glands ofL. stagnalisandBulinus truncatus. The same holds true for haemolymph of infectedL. stagnalis: it did not inhibit the CaFl response in glands ofB. glabrataandB. truncatusand even not in those of a related species (L. ovata). Schistosomins in haemolymph of infectedB. glabrataandB. pfeifferi, on the other hand, seem more related. Both appeared to inhibit the hormone response in glands of the twoBiomphalariaspecies studied. The results indicate that schistosomin in haemolymph of schistosome-infected pulmonate snails, although functionally related, may differ structurally.
Heligmosomoides polygyrus (Nematoda): susceptible and resistant strains of mice are indistinguishable following natural infection
Authors: Scott M. E.
Published: June 2009

BALB/c mice were characterized as more resistant to infection with Heligmosomoides polygyrus (Nematoda) than C57BL/6 mice based on lower establishment and survival during a primary infection and stronger protection induced by an immunizing regime. It was hypothesized, therefore, that C57BL/6 mice would be more heavily infected than BALB/c mice when they lived together as a single population in a large indoor arena where transmission occurred through contact between the mice and damp peat trays where parasite eggs developed into larvae. Fifty female mice (including 5 infected mice) of each strain were placed in a 3.2 x 0.8 m arena. Net egg production and numbers of larvae acquired by sentinel mice of each strain were monitored every two weeks. The experiment was replicated twice. The results did not support the hypothesis. No difference was detected between strains of mice in the number of larvae acquired by sentinel mice during 24 h exposure periods, or in the numbers of worms present after 12 or 23 weeks. Net egg production was also comparable between strains. A hypothesis that the unexpected similarity of infection in the two strains was related to differences in rates of contact with the peat trays was not supported by preliminary data on mouse behaviour that revealed equal frequency of contact with peat trays between strains. A second hypothesis that continuous exposure to larvae led to similar infection levels in the two strains (in contrast to the controlled characterization experiments) was also unsupported. Mice were infected weekly with 10, 50 or 100 larvae for 5 or 10 weeks. Net egg production and numbers of worms were consistently higher in C57BL/6 than BALB/c mice. At this time it is not clear why infection in the two strains was virtually identical in the large arenas but clearly distinct in all controlled infection experiments.
Transmission of taeniid tapeworm eggs via blowflies to intermediate hosts
Authors: Lawson J. R. , Gemmell M. A.
Published: June 2009

Experiments showed that dead blowflies containing eggs of Taenia hydatigena can transmit infection if ingested by lambs during grazing. Rabbits became infected with T. pisiformis after grazing grass exposed to blowflies that had been in contact with dog faeces containing the eggs of this parasite. When captive blowflies were exposed first to dog faeces containing proglottids of T. hydatigena and then to cooked meat, 100% of pigs fed on this meat became infected. The experiments are intended to model the transmission dynamics that result in human larval tapeworm infections. The implications of the results to the epidemiology of human hydatid diseases caused by Echinococcus granulosus and E. multilocularis as well as of T. solium cysticercosis are discussed.
Schistosoma japonicum: some parameters affecting the development of protective immunity induced by a cryopreserved, irradiated schistosomula vaccine in guinea-pigs
Authors: Xu S. , Shi F. , Wu H.
Published: June 2009

Experiments were conducted in guinea-pigs to elucidate the parameters affecting the development of protective immunity against Schistosoma japonicum induced by a cryopreserved, irradiated schistosomula vaccine such as the number of immunizations, route of injection and the use of adjuvants. Results obtained indicated that the cryopreserved, irradiated schistosomula vaccine was effective by either intradermal or intramuscular injection. One intradermal injection with BCG adjuvant resulted in an average worm reduction of 50·24%, only a little lower than that of a non-cryopreserved, irradiated vaccine, 53·55%, with no statistically significant difference between the two. By intramuscular injection the worm reduction was lower (max. 40%) whether given with or without adjuvants or in 1 or 2 injections.
Temperature-dependent reproduction and survival ofGyrodactylus salarisMalmberg, 1957 (Platyhelminthes: Monogenea) on Atlantic salmon (Salmo salarL.)
Authors: Jansen P. A. , Bakke T. A.
Published: June 2009

The relationship of survival and reproduction ofGyrodactylus salarisMalmberg on the Atlantic salmon (Salmo salar) to water temperature (2·5–19·0 °C), was studied on the basis of temporal sequence of births and age at death of individual parasites on isolated salmon, and of infrapopulation growth on isolated and grouped salmon. Mean life-span of the parasite was negatively correlated with water temperature: 33·7 days at 2·5 °C and 4·5 days at 19·0 °C. The average number of offspring per parasite peaked between 6·5 and 13·0 °C, and was approximately 2·4 at these two temperatures. Both the period between the successive births of the offspring (max 4) and the estimated generation time were negatively correlated with temperature. The innate capacity for increase (rm) was positively correlated with temperature: from 0·02 (/parasite/day) at 2·5 °C to 0·22 (/parasite/day) at 19·0 °C. Growth of the infrapopulations was positively correlated with water temperature and was higher on isolated fish than on grouped fish, though less than the potential parasite population growth estimated fromrm. In the infrapopulations the mean intensity of parasites continued to increase throughout all the experiments on both isolated fish and on grouped fish.
The inhibition ofPlasmodium falciparumgrowthin vitroby sera from mice infected with malaria or treated with TNF
Authors: Butcher G. A. , Clark I. A.
Published: June 2009

Despite some years of enquiry, the mechanism that leads to intra-erythrocytic death of malarial parasites during the host's response to infection has not been elucidated. We report here that serum from mice undergoing a successful immune response toPlasmodium chabaudidoes not inhibitPlasmodium falciparumunless thePl. chabaudiis virulent enough to rise to at least 50% parasitaemia and to cause illness. This appears to be true of the 556 KA and DS strains ofPl chabaudi, and also other murine malaria parasites. In mice infected withPl. chabaudi556 KA inhibitory activity coincided with the presence of TNF in their serum. Exogenous TNF generated inhibitory activity in the serum of mice only if the animals were pretreated withProprionobacterium acnes, implying a role for activated macrophages downstream from TNF in this process. The difference in inhibitory activity againstPl. falciparumin serum from mice infected withPl. chabaudiof more or less virulence may be one of degree. Alternatively two distinct mechanisms may operate, the second coming into operation only in ill mice, with higher parasite burdens.
Association between circulating antigen and parasite load in a model filarial system,Acanthocheilonema viteaein jirds
Authors: Harnett W. , Worms M. J. , Grainger M. , Pyke S. D. M. , Parkhouse R. M. E.
Published: June 2009

Jirds (Meriones libycus) were infected with various numbers ofAcanthocheilonema viteaeL3 stage parasites. During the course of the ensuing 16 weeks, blood samples were collected at 2 weekly intervals and the amount of the major parasite excretory–secretory product (E–S 62) and antibodies directed against it measured. After 16 weeks, animals were sacrificed and the size of the mature worm burden established. In spite of interaction between E–S 62 and host antibody, a statistically significant relationship was found to exist between the amount of E–S 62 present in the bloodstream and the size of the parasite load. It is suggested that the detectable antigen level is more influenced by the size of the worm burden than the presence of antibody and that antibody is only likely to affect adversely antigen measurement in situations where the amount released is relatively low. Examples of this are early in infection and in low-level infections. These ideas are discussed in relation to the development and assessment of serological assays which attempt to predict parasite burden in human filarial infections.
The in vitro transformation of the miracidium to the mother sporocyst of Schistosoma margrebowiei; changes in the parasite surface and implications for interactions with snail plasma factors
Authors: Daniel B. E. , Preston T. M. , Southgate V. R.
Published: June 2009

The in vitro transformation of the miracidium to the mother sporocyst of Schistosoma margrebowiei was initiated by placing the miracidium in mammalian physiological saline. The transformation occurs in stages: the cilia cease beating; the ciliated plates become detached from the intercellular ridges and underlying muscle layers; the intercellular ridges spread over the body surface eventually forming a new tegument; the sporocyst changes from an ovoid to a tubular shape in about 48 h at room temperature. The surfaces of the miracidium, sporocyst and cercaria of S. margrebowiei display stage-specific carbohydrates on their surfaces as indicated by lectin staining. Ricin120 stains the cilia alone of the miracidium whereas peanut agglutinin stains the larval surface except for the cilia. The intercellular ridges of the miracidium stain with concanavalin A and wheat germ agglutinin, and these lectins stain the entire surface of the mature mother sporocyst. The cercaria is the only larval stage which stains positively with asparagus pea lectin. Bulinus nasutus is incompatible with Schistosoma margrebowiei; the haemolymph of this snail contains an agglutinin which agglutinates a wide variety of mammalian erythrocytes including those of human ABO blood groups. The haemagglutinin titre of B. nasutus plasma is reduced after incubation with miracidia of S. margrebowiei indicating that the agglutinin is absorbed onto the surface of this larval stage but not that of the mother sporocyst or cercaria. The possible roles of agglutinins in host–parasite interactions together with the significance of the differences in the surface carbohydrates of the larval stages are discussed.
Trypanosoma cruziglutathione-binding proteins: immunogenicity during human and experimental Chagas' disease
Authors: Plumas-Marty B. , Verwaerde C. , Loyens M. , Velge P. , Taibi A. , Cesbron M. F. , Capron A. , Ouaissi M. A.
Published: June 2009

Following purification by affinity chromatography, three glutathione-binding proteins (TcGBP) of 45, 30, and 25 kDa were co-purified fromTrypanosoma cruziepimastigotes. Using 1-chloro-2,4 dinitrobenzene as substrate, a glutathione S-transferase activity of 70 nmol/min/mg of proteins was detected in the GSH binding fraction. An increased expression of TcGBP and total GST activity was observed upon incubation of parasites with phenobarbital, which is an inducer of GST synthesis. Immunofluorescence and electron microscopic experiments demonstrated that TcGBP were expressed by all developmental stages of the parasite, including infective forms. The expression of these proteins by intracellular dividing amastigotes could be in favour of a potential defensive role of these molecules against host attack. Results obtained by immunoprecipitation ofin vitrotranslation products using anti-TcGBP antisera suggested that these three polypeptides are not glycosylated. In addition, antibodies directed against the TcGBP were found in a high proportion ofT. cruzi-infected chronic chagasic patients' sera and in sera of chronically infected BALB/c mice. In contrast, acute chagasic patients' sera and acute-phase mouse sera were found to be poorly reactive with these proteins. Our results identify a new class of potential target antigens, which may be essential for the development ofT. cruziin its host. Their protective role in experimental models deserves to be investigated.
Genetic variation in Trypanosoma brucei and the epidemiology of sleeping sickness in the Lambwe Valley, Kenya
Authors: Cibulskis R. E.
Published: June 2009

A contingency table approach was used to explore the influence of location, host species and time on the genetic composition of a Trypanosoma brucei population in Lambwe Valley, Kenya. Significant differences in zymodeme frequencies were noticed over comparatively short geographical distances suggesting that transmission of T. brucei is somewhat localized. A significant association was observed between zymodeme and the mammalian host from which T. brucei was derived. The association was consistent in different localities in Lambwe valley and remained stable for at least 32 months. These observations indicate that zymodemes are adapted to different host species and that genetic exchange has not disrupted host associations over this time-scale. A major change in the composition of the T. brucei population during a sleeping sickness outbreak in 1980 was confirmed. But while new zymodemes emerged, a decline in overall diversity was noted during times of high sleeping sickness incidence. The results can be explained by selection of T. brucei zymodemes for particular transmission cycles. Although it is not necessary to invoke genetic exchange, sex may help T. brucei to adapt to changes in selection pressures. Such a hypothesis helps to explain why T. brucei appears largely clonal in the short term, even though population studies indicate that sex is responsible for much genetic diversity in the long term. It also explains why neighbouring populations of T. brucei are composed of a different range of zymodemes formed from the same alleles. Such a view implies that genetic exchange has an important role in the microevolution of T. brucei populations.
The laboratory maintenance of Sanguinicola inermis Plehn, 1905 (Digenea: Sanguinicolidae)
Authors: Kirk R. S. , Lewis J. W.
Published: June 2009

Methodology is described for the laboratory maintenance of the life-cycle of Sanguinicola inermis, using common carp (Cyprinus carpio) as the definitive host and Lymnaea peregra as the intermediate host. Lymnaea auricularia was also infected but is not considered to be a suitable laboratory host. Tench (Tinca tinca) were susceptible to infection at high cercarial doses but subsequent infection rates were low. Goldfish (Carassius auratus) and Lymnaea stagnalis were refractory to laboratory infection.
Megasomes as the targets of leucine methyl ester inLeishmania amazonensisamastigotes
Authors: Antoine J.-C. , Jouanne Colette , Ryter Antoinette
Published: June 2009

Certain L-amino acid esters, such as L-leucine methyl ester (Leu-OMe), can kill intracellular and isolatedLeishmania amazonensisamastigotes. Killing appears to involve ester trapping and hydrolysis within an acidified parasite compartment (M. Rabinovitch and S. C. Alfieri, 1987,Brazilian Journal of Medical and Biological Research20, 665–74). We show here by acid phosphatase light microscopic cytochemistry and by ultrastructural morphometry that megasomes, lysosome-like amastigote organelles, are the putative parasite targets of Leu-OMe. This conclusion is supported by the following observations, (a) Control amastigotes displayed a string of electron-dense, acid phosphatase-positive megasomes mostly located in the cellular poles opposite the flagellar pockets. Incubation of the amastigotes with Leu-OMe resulted in concentration-dependent swelling and fusion of the organelles as well as decreased electron density of the internal contents. These changes, which preceded parasite disruption, were followed by the progressive loss of parasite viability and the release of acid phosphatase activity into the medium, (b) Incubation of the amastigotes with L-isoleucine methyl ester, a non-leishmanicidal compound, induced only moderate fusion of the megasomes. (c) Pre-incubation of the parasites with the proteinase inhibitors antipain and chymostatin, previously shown to confer protection from Leu-OMe toxicity, nearly completely prevented the morphological changes of megasomes. (d) Exposure of amastigotes to tryptophanamide (Trp-NH2), the leishmanicidal activity of which is not reduced by antipain and chymostatin, did not result in swelling and fusion of the megasomes. This last finding suggests that different mechanisms underlie the destruction of amastigotes by Trp-NH2 and Leu-OMe. Overall, the results are compatible with the hypothesis that Leu-OMe and other amino acid esters are trapped and hydrolysed within megasomes.
Expression of hybrid malaria antigens in insect cells and their engineering for correct folding and secretion
Authors: Murphy V.F. , Rowan W.C. , Page M.J. , Holder A.A.
Published: June 2009

Hybrid proteins containing selected regions of the major surface antigens of the sporozoite and merozoite stages of Plasmodium falciparum were expressed in insect cells using baculovirus vectors. A recombinant protein containing the signal peptide from the precursor to the major merozoite surface antigens (PMMSA) fused to a fragment from the carboxy (C) terminus of the same gene was recognized by monoclonal antibodies specific for reduction-sensitive conformational epitopes within the C-terminal fragment, suggesting that correct disulphide cross-linking of cysteine residues within this region had occurred. Addition of 26 copies of the tetrapeptide repeat from the circumsporozoite protein (CSP) resulted in a protein recognized by anti-CSP antiserum as well as the conformation specific inonoclonal antibodies. Deletion of the C-terminal putative anchor sequence from both proteins resulted in secretion of protein in a fully soluble form antigenically indistinguishable from the anchor containing products. Correct conformation was not observed when the proteins were expressed as polyhedrin fusions without the signal peptide. These data indicate that the PMMSA signal peptide is recognized in insect cells and that correct assembly of disulphide cross-links is dependent upon targeting the protein to the endoplasmic reticulum.
A basis to extend the proof of migration routes of immature parasites inside hosts: estimated time of arrival of Nippostrongylus brasiliensis and Strongyloides ratti in the gut of the rat
Authors: Tindall N. R. , Wilson P. A. G.
Published: June 2009

The time taken for larvae of Nippostrongylus brasiliensis and a homogonic strain of Strongyloides ratti to complete their migration from the skin surface to the small intestine of the rat was estimated by a new method in which a mirror image of arrival times was created by counting mature parasites at day 8 (N. brasiliensis) or day 5 (S. ratti) in the intestines of rats that had received a single pulse of morantel tartrate by stomach tube at different times starting 10 h after skin application of exact doses of infective larvae. It was confirmed that the effect of the drug was confined to parasites in the gut, so that the kinetics of migration were unperturbed.
Survey of 15 sites over 28 months for entomopathogenic nematodes (Rhabditida: Steinernematidae)
Authors: Hominick W. M. , Briscoe B. R.
Published: June 2009

The presence of entomopathogenic nematodes in soil from 15 sites on 10 sampling occasions over a period of 28 months was documented. Sites were chosen to represent habitats classified as heathland, hedgerow, roadside verge, pasture or woodland. Bioassays utilized Galleria larvae and most of the nematodes obtained were identified asSteinernema (= Neoaplectana) bibionis (Bovien). A sibling species which fails to interbreed with S. bibionis was also found at 2 of the sites. Bioassays were at 15 and 20°C and there was no significant difference in the results at these temperatures. There was no evidence for seasonality in the presence of the nematodes and at 2 sites they were found on every sampling occasion. Otherwise, sites converted unpredictably from positive to negative or negative to positive over the 28-month sampling period.
Effect of selection pressure for thiabendazole resistance on fitness of Haemonchus contortus in sheep
Authors: Maingi N. , Scott M. E. , Prichard R. K.
Published: June 2009

A Strain ofHaemonchus contortusshowing moderate levels of resistance to thiabendazole (TBZ) (egg hatch assay LC50 2.1 μM) was subjected, in alternating sequence, to 5 in vitro and 4 in vivo selections with TBZ. This resulted in a significant increase in resistance (egg hatch assay LC50 2.8 μM). The isolates obtained after each combined in vitro and in vivo selection were compared in terms of egg hatch assay, establishment, net egg output, per capita egg output and degree of pathology caused in infected hosts. The increase in resistance was accompanied by a significant increase in larval establishment sheep (22 %) and was associated with more severe pathology, higher egg count and worm recovery 3 months post- infection.
Phospholipid metabolism in Plasmodium-infected erythrocytes: guidelines for further studies using radioactive precursor incorporation
Authors: Vial H. J. , Ancelin M. L. , Thuet M. J. , Philippot J. R.
Published: June 2009

The biosynthesis of phospholipids is extensive in Plasmodium knowlesi-infected simian erythrocytes due to the synthesis of membranes by this single-cell eukaryote in a host erythrocyte devoid of any pathway for lipid biosynthesis. In the present paper, we show that the incorporation of [3H]glycerol, which reflects de novo biosynthesis, is better studied at 300 μM−1 mM than at the trace doses, since this non-physiological precursor does not modify the amount of phosphatidylcholine biosynthesis from [3H]choline. Time-course incorporation of radioactive glycerol, oleate, lysophosphatidylcholine, choline, and inositol in RPMI 1640 medium containing nutrients for lipid synthesis showed that the optimum incubation time for phospholipid studies is 60–90 min, after which radioactive incorporation slows considerably. On the other hand, studies with [14C]serine revealed that incubation for 2–3 h is necessary for isotopic labelling of phosphatidylcholine via phosphatidylserine decarboxylation and phosphatidylethanolamine N-methylation. Incorporation of the various fatty acids into individual lipids was related to the molecular species composing each of them. Studies with [14C palmitoyl] lysophosphatidylcholine showed a very fast intracellular release of radioactive fatty acids, which indicates a potent lysophospholipase activity. Taken together, these data define the indispensable conditions for an experimental system suitable for further studies.
Ribosomal DNA sequences in the differentiation of pathogenic and non-pathogenic isolates ofEntamoeba histolytica
Authors: Cruz-Reyes J. A. , Spice W. M. , Rehman T. , Gisborne E. , Ackers J. P.
Published: June 2009

Recombinant ribosomal DNA sequences were amplified by PCR and used as probes to perform a fingerprint analysis of total DNA from differentEntamoeba histolyticaisolates. RFLPs obtained with one of the probes, R-1, support previous proposals that pathogenic and non-pathogenicE. histolyticaare closely related, yet genotypically distinct. Another probe, R-2, while not distinguishing between the two forms ofE. hystolytica, was able to differentiate between them andE. moshkovskii, which has morphologically identical cysts and trophozoites. A third probe, BR-1, identified strain-specific RFLPs.
Microhabitat distribution and coexistence of Dactylogyrus species (Monogenea) on the gills of roach
Authors: Koskivaara M. , Valtonen E. T. , Vuori K.-M.
Published: June 2009

The Dactylogyrus fauna was studied from the gills of 293 roach between February 1988 and April 1989. Roach were caught from three interconnected lakes in Central Finland. Nine Dactylogyrus species were found. Of these the seven most abundant were used for studying the abundance of species on different gill-arches, niche breadth and niche overlap between the species. It was found that all species had a species-specific preference for certain gill-arches. The total abundances of all the species went through distinct seasonal changes, peaking during the spring and early summer. Some seasonal variation was also exhibited in gill-arch preferences. Niche breadth and species overlap were mostly higher during the period of peak occurrence of the various species, but in the case of some species they appeared to be unrelated to abundance, indicating possible niche restriction by other species. Most significant was the restriction of D. micracanthus to the fourth gill-arch during the period of peak occurrence of D. similis. Experimental work is needed to verify the reasons for variations in the microhabitat distribution of certain Dactylogyrus species.
Long-term dynamics of natural populations of Schistosoma mansoni among Rattus rattus in patchy environment
Authors: Théron A. , Pointier J. P. , Morand S. , Imbert-Establet D. , Borel G.
Published: June 2009

Dynamics of natural populations of Schistosoma mansoni were studied during 8 consecutive years among Rattus rattus populations from 8 transmission sites of the marshy forest focus of Guadeloupe (French West Indies). The schistosome population is over-dispersed (k = 0·119) within the murine hosts and ecological factors linked to the patchy environment may be responsible for such aggregated distribution. Analysis of the spatio-temporal variations in prevalences, intensities and abundances showed limited variations of the infection during the 8 years at the level of the whole parasite population but great spatial heterogeneity at the level of local schistosome populations. Inter-populational genetic variability linked to the degree of adaptation of this human parasite to the murine host may explain differences in transmission dynamics between the local populations of S. mansoni.
Observations on the development and survival of the free-living stages of Oesophagostomum dentatum both in their natural environments out-of-doors and under controlled conditions in the laboratory
Authors: Rose J. H. , Small A. J.
Published: June 2009

Eggs of Oesophagostomum dentatum in faeces deposited on grass plots from May to October developed into infective larvae. Warm wet weather facilitated development but weather conditions which caused the faeces to dry out rapidly resulted in a heavy mortality of eggs and pre-infective larvae. During the winter no development took place and the eggs died. In the early spring and late autumn a few eggs survived and developed into 1st-stage larvae but they died without developing further. In the laboratory no development took place at 4 °C but at temperatures ranging from 10 to 25 °C development into infective larvae was completed, the rate increasing as the temperature rose. Out-of-doors infective larvae survived in faeces and on herbage for 1 year under a wide range of climatic conditions including the exceptionally cold winter of 1978–79. In the laboratory, infective larvae suspended in water survived even longer at temperatures ranging from 4 to 27 °C. They were rapidly killed by continuous freezing and by desiccation when the relative humidity was less than 90%. The relationship between climatic conditions and the development and survival of the free-living stages is discussed.
Observations on the structure of the male reproductive system and spermatogenesis ofNematodirus battus
Authors: Martin Jean , Lee D. L.
Published: June 2009

In the male reproductive system ofNematodirus battusthe spermatogonia and spermatocytes are arranged upon a central rachis and the spermatocytes are characterized by the presence of cup-shaped membranous organelles which are formed in association with Golgi complexes and granular endoplasmic reticulum. Spermatozoa ofN. battusin the male nematode have an electron-dense, conical tail-like region which contains the nuclear material and an elongate cytoplasmic region which contains the cell organelles. In the uterus of the female, however, the cytoplasmic region of the spermatozoon has an amoeboid appearance and in the seminal receptacle the cytoplasmic region is dome-shaped and many of the membranous organelles have connexions with the outer membrane of the spermatozoa. Movement was not observed in spermatozoa released from the seminal vesicle of the male worm.
Host diet in experimental rodent malaria: a variable which can compromise experimental design and interpretation
Authors: Gilks C. F. , Jarra W. , Harvey-Wood K. , McLean S. A. , Schetters T.
Published: June 2009

Over the past few years several experienced groups studying malaria have encountered significant problems with their particular rodent malaria–host system. This has involved, in some cases, periods during which the recovery of cryo-preserved parasite stocks and growth of bloodstream parasites was markedly inhibited and, in other cases, periods of drastically increased mortality rates. The common factor linking these incidents was that they coincided with alterations in the experimental animal diet used. in the experimental animal diet used. The inhibition of growth of cryopreserved stabilates or bloodstream parasites was abolished by supplementation with p-aminobenzoic acid (PABA) or by changing the diet used. Although the suppressive effects of diets lacking PABA on parasite growth have been known for over 30 years, the variation of PABA levels in modern laboratory animal feed concentrates is not well recognized. We have not established the exact cause of increased mortality, but it has been overcome by changing the diet used. We are documenting our experiences with this potential variable to forewarn workers in other laboratories of possible problems inherent in the use of different diets.
Gastrointestinal hormones: environmental cues for Fasciola hepatica?
Authors: Sukhdeo M. V. K. , Sukhdeo S. C.
Published: June 2009

The effects of pharmacological concentrations of several gastrointestinal hormones on the rate of sucker activity and the frequency and the amplitude of spontaneous longitudinal muscle contractions have been examined in adult Fasciola hepatica. Caerulein and serum decrease the rate of oral sucker activity; motilin decreases and CCK–PZ increases ventral sucker activity when compared to controls. Caerulein, serum and motilin significantly inhibit the frequency of contractions while bile, caerulein and motilin decrease the amplitude of contractions. These results suggest that F. hepatica can recognize and respond to certain gastrointestinal hormones and there may be adaptive value in these behavioural responses.
The relationship between duration of infection with Trypanosoma brucei in mice and the efficacy of chemotherapy
Authors: Jennings F. W. , Whitelaw D. D. , Urquhart G. M.
Published: June 2009

Relapse of infection after drug treatment of trypanosome infections under conditions precluding re-infection has usually been ascribed to drug resistance on the part of the parasite or to under-dosage of the drug. With Trypanosoma brucei infection in mice we have obtained evidence of another type of relapse. In infections resulting from the inoculation of 1 × 105 trypanosomes, derived from a stabilate T. brucei TREU 667, treatment with diminazene aceturate (Berenil) at 40 mg/kg at either 3 or 7 days after infection elicited a permanent cure. If, however, treatment was delayed later than 14 days after infection, then all the mice relapsed. These relapses generally occurred between 20 and 50 days after treatment, but some mice remained aparasitaemic for up to 60 days. The relapsed infections were apparently not due to the survival of ‘drug-resistant’ trypanosomes, as infections derived from a stabilate isolated from a relapsed Berenil-treated mouse were also permanently cured with Berenil if treated 3 days after infection; however, if treatment was delayed until 21 days post-infection, all the mice relapsed. The cause of relapse was not related to the number of parasites inoculated, as infection resulting from initial inocula of 1 × 105 to 1 × 108 trypanosomes were all cured if treated at 3 days after infection, and all eventually relapsed if treatment was delayed until day 21. This type of relapse phenomenon was not confined to T. brucei TREU 667 but also occurred with 5 other stabi-lates of T. brucei after Berenil treatment. Treatment of T. brucei TREU 667 infections with Ethidium and Prothidium at dose levels of 7.5 and 10 mg/kg respectively was also followed by relapse if treatment was delayed for 3 weeks after infection. The possible causes of relapse under these conditions, and its implications in the study of the natural disease, are discussed.
The ultrastructure and histochemistry of the cyst wall of Bucephalus haimeanus (Lacaze-Duthiers, 1854)
Authors: Higgins Jacqueline C. , Wright D. E. , Matthews R. A.
Published: June 2009

Metacercarial cysts of Bucephalus haimeanus occur throughout the liver of Pomatoschistus microps, greater concentrations being found around the gall bladder, blood vessels and periphery of the liver. The cyst wall is composed of three layers, an inner granular, middle vacuolated and outer nucleated layer. The inner layer consists of three zones, an inner zone of irregularly compacted, granular material; a middle densely compacted zone and an outer moderately compacted zone. Vacuoles of the middle layer vary in appearance and appear to be discharging their contents into the cyst cavity. The cells of the outer layer are flattened and elongated with elongate nuclei but no other distinct organelles. Occasionally at the outer edge of the cyst are electron-dense cells which are in the process of degeneration. Only small amounts of collagen and very few leucocytes are associated with the cysts.

The cyst wall is carbohydrate in nature containing some free aldehyde groups, galactogen and neutral mucosubstances. The inner layer appears to consist of mainly acidic mucopolysubstances and weakly acidic sulphomucins. Large amounts of protein, carbohydrate-protein complexes and DNA are also present within the cyst wall. Alkaline and acid phosphatases, ATPase, β-glucuronidase and N-acetyl-β-glucosaminidase were detected. The origin and function of the cyst wall is discussed.
The effect of previous desiccation on the ability of 4th-stage larvae ofDitylenchus dipsacito control rate of water loss and to survive drying
Authors: Perry R. N.
Published: June 2009

The desiccation survival of 4th-stage larvae ofDitylenchus dipsacirevived from dry worm aggregations (‘wool’ larvae) was compared with that of larvae extracted from narcissus bulbs (‘bulb’ larvae). Both sorts survived desiccation well, but ‘wool’ larvae survived desiccation at various humidities somewhat better than ‘bulb’ larvae. The rate of drying of the former was more rapid than that of the latter; the ability to control water loss, therefore, does not of itself ensure survival. The number of larvae reviving decreased with repeated cycles of desiccation and hydration, and also with the increase in the period during which the nematodes were kept dry. However, this was not associated with any loss of ability to control drying. The rate of drying of ‘wool’ larvae remained unaltered irrespective of previous desiccation treatment. In contrast, the rate of drying of ‘bulb’ larvae was more rapid after an initial desiccation with the result that ‘bulb’ larvae dried at the same rate as ‘wool’ larvae. While ‘wool’ and ‘bull’ larvae differed initially in both the rate of water loss and survival, a period of desiccation eliminated only the difference in water loss.

The results suggest that the rate of drying is dependent largely on physical factors. It was shown, however, that the cuticle of dead larvae was completely permeable to water in both directions. Therefore the ability to control water loss must, in some as yet unknown way, be connected with the nematode as a living system.
Alterations in erythrocyte membrane phospholipid organization due to the intracellular growth of the human malaria parasite,Plasmodium falciparum
Authors: Maguire P. A. , Prudhomme J. , Sherman I. W.
Published: June 2009

The asymmetric distribution of phospholipids in the erythrocyte membrane during the intracellular development of the human malaria parasitePlasmodium falciparumwas studied. Infected cells of high parasitaemia were treated with phospholipase A2or sphingomyelinase C, followed by isolation of the host red cell membrane using the Affigel (731) bead method. Additionally, phosphatidylserine on the surface of infected cells was probed using a phosphatidylserine-sensitive prothrombinase assay. Trophozoite-infected cells showed an increase in phosphatidylethanolamine and phosphatidylserine and a decrease in phosphatidylcholine in the outer leaflet. In addition to the changes already present in trophozoite-infected cells, schizont-infected cells showed a decrease in sphingomyelin as well as a further increase in phosphatidylserine in the outer leaflet. The results are discussed with respect to possible mechanisms and consequences of these changes.
Rickettsia-like organisms, puparial temperature and susceptibility to trypanosome infection in Glossina morsitans
Authors: Welburn S. C. , Maudlin I.
Published: June 2009

Maintaining the puparial stage of successive generations of a population of tsetse 3 °C lower than normal reduced the numbers of rickettsia-like organisms (RLO) carried by emerging flies. The susceptibility of these flies to midgut infection with Trypanosoma congolense was also significantly reduced compared with control flies held at normal temperature. These results support the view that the relationship between RLO and susceptibility is quantitative – teneral flies with heavier RLO infections being more susceptible to trypanosome infection.
Synchronized erythrocytic schizogony and gametocytogenesis of Plasmodium berghei in vivo and in vitro
Authors: Mons B. , Janse C.J. , Boorsma E. G. , Van Der Kaay H. J.
Published: June 2009

Both asexual and sexual development of Plasmodium berghei was synchronized without chemical intervention using in vitro culture techniques. Combined in vivo and in vitro experiments were performed on the relationship between age, morphology and maturity of gametocytes. Schizogony took 22–23 h in the experiments. At 26 h post-invasion (p.i) the first males became capable of exflagellation. By 20 h p.i. the first gametocytes were recognizable in Giemsa-stained smears but the sex was hardly distinguishable until maturity (26 h p.i.). Survival time of gametocytes was estimated at 26 h in vitro (half-life 13 h) and the same survival time was suggested for gametocytes in vivo. Schizonts of P. berghei apparently disappeared from the peripheral circulation upon maturity, rupturing almost immediately. Mature schizonts in vitro persisted up to 48 h p.i. in non-agitated cultures. No evidence was collected for sequestration of any sub-population of gametocytes.
Enzyme variation in pathotypes of the potato cyst nematodes Globodera rostochiensis and G. pallida
Authors: Fox P. C. , Atkinson H. J.
Published: June 2009

A total of 65 enzymes in the 8 European pathotypes of the potato cyst nematodes Globodera pallida and G. rostochiensis were examined by isoelectric focusing (IEF) for possible polymorphic variants which may aid rapid pathotype recognition. Quantitative variation was seen with glucose oxidase (EC 1.1.3.4), with high levels of this enzyme present in G. rostochiensis Ro3. Mannose phosphate isomerase (EC 5.3.1.8) also varied between the pathotypes with G. rostochiensis Ro4 and Ro5 differing from the other pathotypes in the relative absorbance of some bands. Phosphoglucomutase was examined on a narrow-range pH gel and additional differences to those described previously were detected.