bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pathways to the impairment of human nutritional status by gastrointestinal pathogens
Authors: Solomons N. W. 
Published: June 2009

SUMMARYGastrointestinal pathogens are of three varieties, those that can, and often do, take the life of the host, those that infect transiently and rarely are life-threatening, and those (parasites) that establish a relatively prolonged residence or colonization of the host's alimentary tract. In the case of the second form, if infections are recurrent, both catabolic effects during the episode and failure to digest foods and/or absorb nutrients result. Similarly, catabolic wastage through activation of the acute phase response, and interference with the host's acquisition of nutrients by maldigestion, malabsorption, intestinal losses and competition with the parasite burden can impair growth and nutrition with helminthic infections. Growth and nutrition with respect to all of the macronutrients and virtually all of the micronutrients have been documented to be adversely affected by gastrointestinal pathogens. For its burgeoning importance as a worldwide health problem, both with the HIV virus as a direct intestinal pathogen and with the opportunistic gut infections occurring in the immunocompromised host, AIDS represents the emerging context of the impairment of nutritional status by intestinal pathogens.
Malarial parasites and antioxidant nutrients
Authors: Levander O. A. , Ager A. L. 
Published: June 2009

SUMMARYSusceptibility to oxidative stress is a well-established feature of the malarial parasite. Pharmacologists have taken advantage of this property to design highly effective pro-oxidant antimalarial drugs. Less well appreciated is the fact that nutritional manipulation of host oxidative stress status by dietary means can have a profound effect on the growth of the parasite. In particular, rapid induction of vitamin E deficiency in mice by feeding highly unsaturated fatty acids (fish oil) strongly suppresses plasmodial growth. Likewise, the status of other antioxidant nutrients (e.g., riboflavin or vitamin C) may also influence the course of malarial infection under certain conditions. A combined nutritional pharmacology approach may offer some promise in controlling malaria.
Trans-sialidase, SAPA amino acid repeats and the relationship betweenTrypanosoma cruziand the mammalian host
Authors: Frasch A. C. C. 
Published: June 2009

SUMMARYDuring invasion of multicellular organisms, protozoan parasites expose functional molecules that become targets for the host immune response. Recent research onTrypanosoma cruzi, the agent of Chagas' disease, suggests a new model of how the parasite might deal with this problem. Several antigens ofT. cruzihave tandemly repeated amino acid motifs in molecules with as yet unknown functions. In two cases, these repeats are in molecules with a defined structure or function. Both proteins are implicated in the invasion of host-cells by the parasite. One of these is the core protein of a putative mucin-like glycoprotein that has Thr/Pro–rich repeats which, by themselves, might define the structure of a highlyO-glycosylated molecule. The other protein is SAPA/trans-sialidase/neuraminidase, a molecule able to transfer sialic acid, that has so far only been described in trypanosomes. The amino acid repeats present in SAPA/trans-sialidase/neuraminidase are unrelated to the enzymic activity and constitute an immunodominant C–terminal domain. The N–terminal domain of SAPA/trans-sialidase/neuraminidase controls the enzymic activity since a recombinant molecule lacking the repeats conserves trans-sialidase activity. That both domains are functionally independent is also indicated by experiments that show that antibodies directed against the amino acid repeats are unable to inhibit trans-sialidase activity. A large number of proteins having trans-sialidase related sequences but lacking enzymic activity are also present in the surface membrane of the parasite. The immunodominant SAPA/trans-sialidase/neuraminidase repeats, together with the complex network of cross-reacting epitopes present in related but enzymically inactive proteins might contribute to the delay in mounting an effective antibody response. However, antibodies neutralizing trans-sialidase activity are generated later during the infection. These antibody specificities are directed to the enzymic domain of the molecule and might contribute to the control of parasite dissemination after the early period of the infection.
Changes in parasite aggregation with age: a discrete infection model
Authors: Quinnell R. J. , Grafen A. , Woolhouse M. E. J. 
Published: June 2009

SUMMARYWe present a discrete time model for age-related changes in the mean and variance of the number of helminth parasites per host. We assess the degree of aggregation as the negative binomial parameter,k, and use the model to examine the influence of various factors on changes in aggregation with host age: discrete versus continuous infection; the degree of predisposition to infection; infection rate; parasite survival rate; and the variance in exposure to infective stages. The model can produce both increases and decreases inkwith host age. However, with parameter values typical of many human helminth infections, a monotonic increase ink(decrease in aggregation) with age is predicted. With an age-dependent infection rate, convex relationships betweenkand age are possible. These predictions are consistent with data from field studies, but differ from those of previous models which have suggested thatkis independent of host age in the absence of density dependence in parasite population dynamics. Differences between the models, and some difficulties in the interpretation of field data, are discussed.
The effect of the sulphoxide metabolite of triclabendazole (‘Fasinex’) on the tegument of mature and immature stages of the liver fluke, Fasciola hepatica
Authors: Stitt A. W. , Fairweather I. 
Published: June 2009

SummaryThe effects of the novel benzimidazole, triclabendazole (TCBZ) (‘Fasinex’, Ciba-Geigy), in its active sulphoxide metabolite form (TCBZ-SX), on the tegumental ultrastructure of Fasciola hepatica were determined in vitro by transmission electron microscopy (TEM), using both intact flukes and tissue-slice material. At a concentration of 15 µ/ml, the tegument of the whole adult fluke showed ultrastructural changes only after prolonged time-periods, with vacuolation at the base of the syncytium and accumulation of T2 secretory bodies in the tegumental cells. At a concentration of 50 µ/ml, with both whole flukes and tissue-slices, the tegument appeared extremely abnormal with accumulation of secretory bodies towards the base of the syncytium. With longer incubation times, the tegument was completely sloughed away and the tegumental cells became synthetically inactive. The tegument of the 3-week-old juvenile became progressively convoluted at the apex, while in the basal regions there was severe vacuolation. In the tegumental cells, there were accumulations of T1 secretory bodies. These results confirm TCBZ as a potent fasciolicide, being very effective in disrupting the fluke tegument. They may go some way to explain the mode of action of this important fasciolicide.
Characterization of the effector mechanisms of a transmission-blocking antibody upon differentiation ofPlasmodium bergheigametocytes into ookinetesin vitro
Authors: Ranawaka G. R. R. , Alejo-Blanco A. R. , Sinden R. E. 
Published: June 2009

SUMMARYThe transmission-blocking monoclonal antibody 13.1, which recognizes the ookinete surface antigen Pbs21 ofPlasmodium berghei, and an IgG2a isotype control antibody 26.37 were purified by caprylic acid and ammonium sulphate precipitation. Fab fragments were prepared by papain digestion. IgG but not Fab from antibody 13.1 reduced ookinete formation byP. bergheiin culture by as much as 94% at a concentration of 100 μg/ml. There was little difference in antibody efficacy in the range 6·25–400 μg/ml in this assay. The parasite was most sensitive to antibody activity in the first 6–9 h of culture, i.e. the gamete/zygote and early retort stages. Peripheral blood leucocytes (PBL) were essential to achieve maximal inhibition by mAb 13.1 (activity was abrogated totally if PBL were removed). Together the data suggest that one of the mechanisms of action of this antibody is antibody-mediated PBL killing. Phagocytosis of parasites was noted in these experiments in all cultures. We have not attempted in this study to distinguish between Fc-mediated opsonization, as opposed to antibody-dependent cellular cytotoxicity.
Density-dependent regulation of the growth of the hookworms Necator americanus and Ancylostoma ceylanicum
Authors: Norozian-Amiri S. M. B. , Behnke J. M. 
Published: June 2009

SUMMARYLaboratory bred DSN hamsters were exposed to varying doses of infective larvae of Ancylostoma ceylanicum (orally) or Necator americanus (percutaneously) and were autopsied at times which corresponded to a period immediately before cessation of growth of worms or soon afterwards. A total of 829 (404 male and 425 female) A. ceylanicum and 1582 (781 male and 801 female) N. americanus were measured. At worm burdens of fewer than 100, the length of A. ceylanicum appeared to increase with infection intensity and no evidence was found that growth was retarded under crowded conditions. In an experiment comparing directly low (mean worm burden = 22) and heavy infections (mean worm burden = 180) significant negative associations between both weight and width, and worm burden were detected, but length again increased with worm burden. In contrast, 5 experiments with N. americanus indicated negative relationships between measures of worm size (length, width, wet and dry weight) and worm burden. It was concluded that N. americanus is subject to regulation by density-dependent processes within the host while A. ceylanicum is not sensitive to the same degree.
The effects of Onchocerca lienalis infection on vitellogenesis in the British blackfly, Simulium ornatum
Authors: Renshaw M. , Hurd H. 
Published: June 2009

SummaryWe have previously described the major yolk protein, vitellin, in the British blackfly Simulium ornatum Meigen. Here we demonstrate that vitellogenin, synthesized in the fat body and secreted into the haemolymph, is composed of subunits with the same approximate molecular weight as vitellin, namely 200 and 68 kDa. Simulium ornatum is the natural vector for the cattle filarial nematode Onchocerca lienalis Stiles, which induces host fecundity depletion. A significant reduction in ovarian vitellin content was associated with infection by intrathoracic injection of 20 O. lienalis microfilariae immediately after blood-feeding. Fat body synthesis of vitellogenin was significantly reduced as early as 8 h post-infection in comparison with sham-injected flies. When total haemolymph protein from infected and sham injected flies was compared, titres were significantly depressed 6 h post-infection. However, later in the infection, titres were elevated by 30%, the major component being vitellogenin. The injection of dead microfilariae had no effect. An infection burden of a single parasite caused a significant reduction in ovarian protein content in comparison with shams, but no further significant decrease was observed as the parasite burden was increased from 5 to 20. Possible mechanisms underlying the disturbance of Simulium reproductive physiology are proposed.
Responses of the fish ectoparasite Salmincola edwardsii (Copepoda) to stimulation, and their implication for host-finding
Authors: Poulin R. , Curtis M. A. , Rau M. E. 
Published: June 2009

SUMMARYThe short-lived infective copepodid stages of the copepod Salmincola edwardsii, ectoparasitic on brook trout, Salvelinus fontinalis, are under strong selective pressure to evolve efficient host-finding mechanisms. In laboratory experiments, we quantified the effects of visual and mechanical stimulation on the activity of the copepodids. We found that shadows passing above the copepodids and shock waves passing through the water generated marked increases in the rate and length of upward swimming bursts, which resulted in more time spent suspended in the water column and greater distances travelled. However, we found no strong evidence for a relationship between the magnitude of the copepodids' response and the intensity of stimulation. Although these responses are not host-specific, they allow the parasites to conserve their limited energy stores by increasing their host-finding activity only when potential hosts are nearby.
Pseudechinoparyphium echinatum (Digenea: Echinostomatidae): experimental observations on cercarial specificity toward second intermediate hosts
Authors: McCarthy A. M. , Kanev I. 
Published: June 2009

SUMMARYInfectivity of Pseudechinoparyphium echinatum cercariae to 11 species of gastropod was examined experimentally. Broad specificity and differential host—parasite compatibility were exhibited. Nine gastropod species functioned as second intermediate hosts. Planorbarius corneus, Physa fontinalis, Lymnaea peregra and Biomphalaria alexandrina showed high levels of compatibility with the parasite. In single-species exposures over 90% of cercariae encysted in each of these hosts. Low compatibility with the first intermediate host species Lymnaea stagnalis may be a mechanism preventing super-infection of emitting snails. Cercariae did not infect the prosobranchs Bithynia tentaculata and Viviparus viviparus. Experimental infection of a host community comprised of 8 European gastropod species revealed an order of host utilization similar to that shown in single-species exposures. However, cercarial transmission success in P. fontinalis and L. peregra (compared to that in P. corneus) was significantly reduced. This may have been due to the marked preference to cercariae for P. corneus compared to the other two highly suitable hosts for whom cercariae showed equal preference.
Studies on infection and reinfection by eugregarines
Authors: Harry Owen G. 
Published: June 2009

SUMMARYReinfection of the insects Tenebrio molitor and Schistocerca gregaria by the Eugregarines Gregaria polymorpha and G. garnhami respectively is not caused by the retention of the gametocyst and the release of sporocysts inside the gut. The gametocyst has to pass out from the insect gut, dehisce, and the sporocysts have to be ingested in order for reinfection to occur. Thus it is possible to stop reinfection by preventing the host from ingesting sporocysts. The development of spore ducts on the gametocyst of G. garnhami is inhibited if the gametocysts are prevented from leaving the hindgut of the locusts.I would like to thank Professor L. H. Finlayson for his advice for many helpful discussions.
Effects of different levels of nutrition and continuing dosing of poultry with Ascaridia galli eggs on the subsequent development of parasite populations
Authors: Ikeme M. M. 
Published: June 2009

SUMMARYThe population dynamics of Ascaridia galli infections of poultry was studied under repeated doses of 10, 100 and 1000 eggs. Daily doses were continued for 6 weeks only. At low dose rates patency is noted by the fifth week. At higher dose rates there is an accumulation of larvae whose development has been arrested at a precise developmental stage, i.e. the third larval stage. Sporadic development of some of these larvae to adults occurs later. Arguments are produced to show that this inhibition of larval development is a resistance and not a density-dependent phenomenon. The epidemiological significance of this inhibition is discussed. This resistance phenomenon is shown to occur in single infection experiments where 1000 eggs were used. This gives rise to the development of a worm population of two facies. The whole finding is suggested to be related in some way to the phenomenon of ‘tissue phase’, which is accepted as a normal life-cycle behaviour of this parasite. A brief review of previous work on this is given and it is postulated that the ‘tissue phase’ phenomenon is not an obligatory part of the normal life-cycle of the parasite but represents a reaction to factors of resistance inherent in chickens and controlled to a large extent by a complex dynamic interplay of dose size and the chickens.I wish to thank the Department of Technical Co-operation and the Federal Government of Nigeria for financing this project, Dr Boulton of the Poultry Research Centre, Edinburgh, for advice on nutrition, and the Department of Zoology, especially Dr J. A. Campbell, University of Edinburgh, for facilities and advice on the work. I am greatly indebted to the Ministry of Agriculture, Fisheries and Food, Poultry Research Laboratories, Lasswade, for the free supply of chickens used in this work.
Variations in the fecundity of strongylid worms of the horse
Authors: Ogbourne C. P. 
Published: June 2009

SUMMARYA large proportion of Strongylus vulgaris, S. edentatus and Trichonema nassatum collected from the gut lumen of slaughtered horses during the winter did not contain eggs. The proportion of Trichonema catinatum without eggs declined to a low level during the winter and rose to relatively high levels during the summer, It has been concluded that worms without eggs are newly matured individuals and that seasonal variations in fecundity reflect similar fluctuations in the age distribution of the adult populations. These fluctuations are related to seasonal differences in the numbers of infective larvae ingested and to the length of parasitic development.Most Strongylus vulgaris, S. edentatus and Trichonema nassatum reach the adult stage during the winter and it has been suggested that an increase in worm numbers during this period is responsible for a rise in the faecal egg counts of horses in the spring. The observations on T. catinatum indicate that the level is maintained by the arrival of new individuals during the summer.I wish to thank Dr H. D. Crofton for his constant advice and encouragement during this work and Professor H. E. Hinton, F.R.S., for the provision of laboratory facilities. I am indebted to Mr L. J. Potter for allowing me to collect the parasites from his slaughterhouse at Bishop Sutton, near Bristol. This work was carried out during a research studentship funded by the Horse Race Betting Levy Board.
The effect of density of first-stage larvae of Elaphostrongylus rangiferi on the infection rate in the snail intermediate host
Authors: Skorping Arne 
Published: June 2009

SUMMARYThe relationship between the density of lst-stage larvae of Elaphostrongylus rangiferi on the infection rate into the gastropod intermediate host, Arianta arbustorum, was studied experimentally. Within a range of densities between 30 and 1100 larvae/cm2 the experimental data gave a good fit to the conventional epidemiological assumption of direct proportionality between the net infection rate and the density of infective stages. The instantaneous rate of infection was estimated to be about 1 × 10−3/larvae/snail/2 h. At higher densities (> 1100 larvae/cm2) the instantaneous rate of infection showed a densitydependent decline.
Cercaria vaullegeardi Pelseneer, 1906 (Digenea: Hemiuridae); the infection mechanism
Authors: Matthews B. F. 
Published: June 2009

SUMMARYThe inoculative mechanism whereby cystophorous cercariae infect the copepod 2nd intermediate host is described for the first time in Cercaria vaullegeardi. Experimental infections of the harpacticoid copepod Tigriopus brevicornis are recorded and the infection process is related to the ultrastructure of the cercaria and to the feeding mechanics of harpacticoids. The cystophorous tail of C. vaullegeardi is shown to be a device whose shape and construction ensure that the cercarial body is neither damaged by copepod mouthparts nor swallowed, but reaches the host haemocoel during the initial stages of feeding. The cystophorous tail consists essentially of a caudal cyst, into which the cercarial body retracts at encystment, and various appendages including a delivery tube. The infection mechanism is triggered when the copepod mandibles bite the narrow posterior caudal cyst beak, when the delivery tube everts into the mouth and penetrates the dorsal mid-gut wall. The cercarial body, lubricated by tegumental secretions, passes simultaneously through the delivery tube and is inoculated into the host haemocoel.
A putative Leishmania panamensis/Leishmania braziliensis hybrid is a causative agent of human cutaneous leishmaniasis in Nicaragua
Authors: Belli A. A. , Miles M. A. , Kelly J. M. 
Published: June 2009

SUMMARYAs part of a survey of human leishmaniasis in Nicaragua we examined phenotypic and genotypic characteristics of 40 Leishmania isolates. We identified 3 distinct parasites associated with cutaneous disease in this area; Leishmania panamensis (40% of cases), Leishmania braziliensis (33%), and a strain which exhibits the heterozygous isoenzyme and DNA fingerprinting patterns expected of a L. panamensis/L. braziliensis hybrid (27%). There was complete correlation between the isoenzyme and DNA data for each of the putative hybrids examined. All of the ‘hybrids’ were obtained from foci in the northern region of the country where L. panamensis and L. braziliensis occur sympatrically. These observations provide strong evidence for sexual reproduction in New World Leishmania populations and suggest that it is of taxonomic and epidemiological significance.
The ultrastructural localization of Echinococcus granulosus antigen 5
Authors: Jones M. K. , Zhang L.-H. , Leggatt G. R. , Stenzel D. J. , McManus D. P. 
Published: June 2009

SUMMARYMurine monoclonal and polyclonal antisera, raised against the 38 kDa subunit of Echinococcus granulosus antigen 5, were used to investigate the tissue distribution of the antigen in hydatid cysts. Immunoreactivity was visualized by indirect immunofluorescence on whole protoscoleces, and ultrastructural immunocytochemistry utilizing colloidal gold-based labelling procedures on unsectioned and cryosectioned brood capsules and protoscoleces. In protoscoleces, the 38 kDa subunit of antigen 5 was localized at the interface of parenchymal cells and associated extracellular matrices, as well as along the interface of the tegumentary syncytium in the somal region and its basal matrix. Cytoplasmic labelling of parenchymal cells was rare; when observed, it was associated with vesicles and membranes in cytoplasmic extensions of parenchymal cells. In brood capsules, the antigen was associated with the external face of the plasma of degenerating parenchymal cells. The 38 kDa subunit occurs along the extracellular face of cell membranes, suggesting that antigen 5 is either a component of the membranes or associated extracellular matrices.