bluuebunny/crossref_metadata_2025_split huggingface dataset:
Regional versus local helminth parasite richness in British freshwater fish: saturated or unsaturated parasite communities?
Authors: Kennedy C. R. , Guégan J.-F. 
Published: June 2009

SUMMARYThe relationships between regional species richness and local species richness were examined in respect of helminth parasite communities in 32 species of freshwater fish in the British Isles. Fish were divided into 5 categories, for each of which the goodness of fit of the relationship to linear, exponential and power function models was tested. For all categories of fish combined, there was a significant, positive curvilinear relationship. Nested within this were two other patterns. For introduced fish, a linear model provided the best fit; for euryhaline and relict species it was impossible to determine the best model, but for the other categories the relationship was curvilinear and was best fitted by a power function model. The linear relationship found for introduced fish was interpreted as a temporary situation, reflecting the shortage of time for the communities to become saturated. It corresponded to the linear part of the curvilinear relationship of the other categories, which is believed to represent the fundamental form of the relationship for parasite communities. The communities reached a saturation level of richness, corresponding to the asymptote of the curve, which fell well below regional species richness. Explanations for local saturation are discussed, but neither community structure nor supply-side ecology can yet be preferred. It is concluded that local patterns in helminth community richness, in contrast to those in fish assemblages, are not significantly influenced by patterns on a larger, regional spatial scale and so regional species richness is not a key determinant of local species richness, nor does a knowledge of regional patterns improve predictability of local patterns.
Immunocytochemical localization of serotonin (5-HT) in the nervous system of the hydatid organism, Echinococcus granulosus (Cestoda, Cyclophyllidea)
Authors: Brownlee D. J. A. , Fairweather I. , Johnston C. F. , Rogan M. T. 
Published: June 2009

SUMMARYThe localization and distribution of the serotoninergic components of the nervous system in the hydatid organism, Echinococcus granulosus, were determined by immunocytochemical techniques in conjunction with confocal scanning laser microscopy (CSLM). The distribution of serotonin immunoreactivity (IR) paralleled that previously described for cholinesterase activity, although it was more widespread. Nerve cell bodies and nerve fibres immunoreactive for 5-HT were present throughout the central nervous system (CNS), occurring in the paired lateral, posterior lateral and rostellar ganglia, their connecting commissures and nerve rings in the scolex and in the ten longitudinal nerve cords that run posteriorly throughout the body of the worm. A large population of nerve cell bodies was associated with the lateral nerve cords. In the peripheral nervous system (PNS), immunoreactive nerve fibres occurred in well-developed nerve plexuses innervating the somatic musculature and the musculature of the rostellum and suckers. The genital atrium and associated reproductive ducts were richly innervated with serotoninergic nerve cell bodies and nerve fibres.
Studies on the nutrient uptake by the beet cyst nematodeHeterodera schachtiibyin situmicroinjection of fluorescent probes into the feeding structures inArabidopsis thaliana
Authors: Böckenhoff A. , Grundler F. M. W. 
Published: June 2009

SUMMARYA method was developed, which enables substances to be injected into the feeding structure (syncytium) established byHeterodera schachtiiin roots ofArabidopsis thaliana. The technique was used to study the uptake of nutrients by the feeding nematode. The fluorescent dye lucifer yellow CH (LYCH) and fluorescence-labelled dextrans of different molecular weights were injected into the thin and translucent roots ofA. thaliana. Such roots are a feature of this plant and they provide optimal conditions for microinjection. Injected LYCH was taken up by feeding juveniles and adults, indicated by the staining of the alimentary duct and the digestive system. Fluorescent dextrans of 3, 10 and 20 kDa but not of 40 and 70 kDa were ingested, suggesting that molecules of a maximum Stokes radius of 3·2 to 4·4 nm are taken up. It is likely that the feeding tube, forming the interface between the plant cytosol and the nematode's digestive system, is responsible for this size exclusion effect. The injected fluorescent substances were not detected in plant cells adjacent to the syncytium or in the root vascular elements. Injections into parts of roots which were infested by several nematodes revealed that feedingH. schachtiiindividuals may share one syncytium.
Superoxide dismutase (SOD) activity ofDictyocaulus viviparusand its inhibition by antibody from infected and vaccinated bovine hosts
Authors: Britton C. , Knox D. P. , Kennedy M. W. 
Published: June 2009

SUMMARYThe presence of superoxide dismutase (SOD) activity in the bovine lungwormDictyocaulus viviparuswas examined using the xanthine–xanthine oxidase assay system and by non-denaturing PAGE followed by specific enzyme staining. High levels of activity were detected in excretory–secretory (ES) products of adult worms and in soluble extracts of both the L3 and adult stages of the parasite. Stage-specific and ES-specific activities were indicated by differences in SOD isoenzyme profiles between adult and larval parasite extracts and between adult extract and ES products, with a fast migrating activity being specific to ES products. All isoenzymes were sensitive to cyanide, indicating copper/zinc dependency. The antigenicity of ES SOD was demonstrated by a reduction in SOD activity in both the chemical assay and non-denaturing PAGE following incubation of parasite ES products with IgG antibody purified from serum of infected or vaccinated bovine hosts. The high level of SOD activity released by adultD. viviparusmay be a reflection of the problems faced by a parasite occupying an oxygen-rich environment. Antibody inhibition of SOD may, therefore, be an important target of protective immunity.
Immunogenicity of a hybridPlasmodium falciparum, malaria antigen
Authors: Lockyer M. J. , Cooper H. , Tite J. , Rowan W. , Crowe J. S. 
Published: June 2009

SUMMARYA recombinant baculovirus-expressed hybrid protein containing epitopes for the C-terminal fragment of thePlasmodium falciparumprecursor to the major merozoite surface antigens (PMMSA) and the tetrapeptide repeats of the circumsporozoite protein (CSP) was assessed for its immunogenicity. Murine MHC-II restriction of the antibody response to the CSP repeats was not overcome by the PMMSA component, the response to which showed no restriction. In an adjuvant trial the highest antibody titres in rabbits to both components of the hybrid were obtained using Freund's adjuvant. Lack of a boosting antibody response to the CSP repeats appeared to be linked to the conformation of the PMMSA component. Formulation of the hybrid protein into Iscoms gave antibody titres of only short duration to both components.
Population dynamics ofTheileria sergentiin persistently infected cattle and vector ticks analysed by a polymerase chain reaction
Authors: Kubota S. , Sugimoto C. , Onuma M. 
Published: June 2009

SUMMARYTheileria sergentiShintoku stock consists of 2 parasite populations bearing 2 atlelic forms of p33/32, an immunodominant piroplasm surface protein. Parasite population changes during parasite passages among cattle and tick vectors, and during persistent infection in individual calves were analysed by using allele-specific polymerase chain reaction (PCR). The parasite DNAs were prepared from piroplasms from calves which had been infected with Shintoku stock by inoculation of sporozoite stabilates or parasitized erythrocytes, and from sporozoite stabilates which had been prepared from Shintoku stock-infected ticks. Changes in a dominant parasite population were demonstrated during transmission from calves to vector ticks and from infected ticks to calves. Parasite population changes were also apparent during persistent infection in cattle over several months, and this change is thought to occur under host immune pressure. The results of this study indicate that expression of diverse forms of p33/32 may play a role in parasite persistence within mammalian hosts and its transmission from tick vector.
Trypanosoma brucei s.1.: evolution, linkage and the clonality debate
Authors: Stevens J. R. , Tibayrenc M. 
Published: June 2009

SUMMARYThe Index of Association (IA) has been proposed by Maynard Smith et al. (1993) as a general method for characterizing the population structures of microorganisms as either: clonal, epidemic, cryptic species or panmictic. With reference to the current debate surrounding the mode of reproduction in parasitic protozoa, this study explores (i) the suitability and limitations of the IA for characterizing populations of Trypanosoma brucei s.l., and (ii) the idea that the significance of genetic differences between populations may be better understood if the evolution, spread and temporal stability of certain parasite genotypes are also considered. Four populations of T. brucei from Côte d'Ivoire, Uganda and Zambia are analysed using the IA and a complementary test for linkage disequilibrium, test f of Tibayrenc, Kjellberg & Ayala (1990). The two populations from Uganda are characterized as epidemic, while the others appear more or less clonal; the merits of the two methods are compared. The implications of the various population classifications are discussed with reference to genotype longevity in each region; the evolutionary and biomedical consequences of the genetic non-homogeneity of T. brucei are reviewed.
The excystment, growth and reproduction of Acanthoparyphiutn spinulosum Johnston, 1917 (Trematoda) in chicks fed various diets
Authors: Little John W. 
Published: June 2009

Studies have been made of the growth and excystment of a trematode, Acanthoparyphium spinulosum, in chicks fed on various denned diets.Day-old chicks were fed metacercariae and maintained on deficient as well as complete rations for periods up to 20 days. The excystment rate was determined by the number of worms that were recovered from the metacercariae. The largest number of worms were recovered from chicks that received a normal diet with starch as the sole carbohydrate source. The smallest percentage of parasites was found in birds that had received a normal diet with sucrose serving as the carbohydrate source. About 25 % were recovered from chicks fed several other diets.The trematodes developed and grew well in vitamin A deficient chicks; there was a large number of intra-uterine ova observed in worms from these hosts. Acanthoparyphium spinulosum from chicks fed a ‘no vitamin D’ diet grew at a normal rate until the 6th day; after this they grew more slowly than 6-day-old worms in chicks fed the ‘no vitamin A’ diet.The lengths of worms from birds deprived of all vitamins differed little from those of the parasites recovered from the chicks deficient in vitamin D. The largest worms were obtained from chicks fed a complete diet with starch as the sole carbohydrate source.Parasites from chicks fed a diet 50 % deficient in carbohydrates (with sucrose as the carbohydrate) developed normally.Worms also developed in chicks fed a ‘no protein’ diet with starch and a ‘no protein’ diet with sucrose. A deleterious effect on ova production was observed in worms from both these groups.Metacercariae developed in chicks fed a ‘no carbohydrate’ diet, but no mature worms were recovered due to the reduced life of the host. Starvation of the hosts produced small worms containing few intra-uterine ova.The growth curve of A.spinulosum was plotted and compared with Echino-paryphium flexum.This investigation was supported in part by U.S. Public Health Service Grant UI-00202, and by a grant-in-aid of research by the Society of the Sigma Xi, New Haven, Connecticut.
Studies on the structure and hatching of the eggs of Schistosoma mansoni
Authors: Kusel J. R. 
Published: June 2009

The structure and function of the vacuoles in the eggs of Schistosoma mansoni is unknown. In this study the eggs have been immersed in serum albumin and examined by phase-contrast optics. Under these conditions the vacuoles exhibit a definite internal structure, suggesting that they may be or may have been cellular. Histochemical staining techniques to detect the nature of the vacuolar contents revealed that the vacuoles stained heavily with iodine and gave a positive PAS reaction. This suggested the presence of carbohydrate. Stains for nucleic acids, protein and lipid were not taken up by the vacuoles. The egg shell stained with o–toluidine blue and with basic fuchsin uniformly, except for a thin irregular band which might indicate a possible line of weakness. The vacuolar membranes seem to be similar to the vitelline membrane in permeability to hydroxyl ions and it is possible that these membranes have a common origin. Plasmolysis studies with salts, urea, glycerol and sucrose showed that the vacuolar membranes have about the same permeability properties to these compounds as the other egg membranes. Glycerol treatment of the eggs until equilibrium is attained, followed by transfer of the eggs to water or saline results in a hatching of the eggs. In this, a dead mira-cidium is extruded from the shell. Similar treatment of eggs equilibrated with sucrose does not result in this hatching process. It is postulated that glycerol solubilizes a factor which aids the hatching process.I should like to thank the following: Dr S. A. Ibrahim, in whose department this work was carried out; Dr S. Dawood of the Stack Laboratory, Khartoum, who kindly made his microscope available for use; Mr J. R. Lauder for valuable discussions and suggestions; and many young patients in Khartoum Civil Hospital for stool samples and smiles.
Action of pyrimethamine and related drugs againstPlasmodium knowlesi in vitro
Authors: Gutteridge W. E. , Trigg P. I. 
Published: June 2009

A dihydrofolate reductase has been isolated from free-parasite preparations of the primate malarial parasite,Plasmodium knowlesi. Its properties are similar to those reported for the enzyme from the rodent malarial parasite,P. berghei,even though the base compositions of the DNA of these two species are quite different. TheKmsfor substrate and cofactor are 3 × 10−6Mand 1 × 10−6Mrespectively and the molecular weight is ˜ 200000. Concentrations of pyrimethamine and trimethoprim as low as 1 × 10−9Mand 3 × 10−8Mrespectively are sufficient to cause 50% inhibition of enzyme activity. The sensitivity to inhibition by pyrimethamine and trimethoprim of growth of cultures ofP. knowlesihas also been investigated. Preliminary experiments showed that it was only the schizont stage that was susceptible to the action of the drugs and that in their presence, normal nuclear divisions and segmentation did not occur and subsequently, no reinvasion of fresh red cells took place. The minimum concentrations of drug required to produce these effects were 10−9Mfor pyrimethamine and 10−7Mfor trimethoprim. Thus, there is a close correlation between the concentrations of pyrimethamine and trimethoprim required to inhibit the dihydrofolate reductase in a cell-free system and the growth of the parasitein vitro. Pyrimethamine (10−9M) did not, however, affect the incorporation of radioactive precursors into DNA, RNA or protein of schizont stage parasites until after morphological damage could be seen and reinvasion was complete in control cultures. The time courses of incorporation of [14C]algal protein hydrolysate into protein in the presence (10−9M) or absence of pyrimethamine are the same as those described recently with immune serum. The possibility is thus raised as to whether pyrimethamine and immune serum act in the same way.One of us (P.I.T.) received financial assistance from the World Health Organization. We thank Dr F. Hawking for many helpful discussions, Miss Jane Dunnett and Mr T. Scott-Finnigan for technical assistance and Dr O. D. Standen for samples of pyrimethamine and trimethoprim.
Physiology and pharmacology of turbellarian neuromuscular systems
Authors: Blair K. L. , Anderson P. A. V. 
Published: June 2009

SUMMARYOur understanding of the neurobiology of the Platyhelminthes has come in large part from free-living turbellarians. In addition to providing considerable information about the capabilities of the rudimentary nervous system present in all members of the phylum, turbellarians have provided the most definitive information about the variety of ion channels present in the membranes of neurones and muscle cells, and about the physiology and pharmacology of those channels. Furthermore, preparations of single, viable muscle cells have provided some of the most conclusive evidence about the variety of transmitters present, and the types of response they evoke. Here, we review what is known about the physiology and pharmacology of the turbellarian neuromuscular system. Particular attention is given to the triclad flatwormBdelloura Candida, the best studied species in this respect, but other species are included where relevant.
Neuromuscular physiology and pharmacology of parasitic flatworms
Authors: Pax R. A. , Day T. A. , Miller C. L. , Bennett J. L. 
Published: June 2009

SUMMARYThe trematode and cestode flatworms include numerous parasitic forms of major medical and economic importance. A better knowledge of the neuromuscular physiology of these animals could lead to development of new control measures against these parasites. Since these animals are near the stem from which all other animals have evolved, better knowledge of these animals could also yield valuable information about the early evolution of nerve and muscle systems in the animal kingdom. This review focuses on what is known about the characteristics of the somatic muscle in these animals. The anatomy of the muscles is described along with a review of current information about their electrophysiology, including descriptions of the ion channels present. Also included is a summary of recently acquired data concerning the nature of serotonin, peptide, acetylcholine and glutamate receptors on the membranes of the muscles.
The motornervous system ofAscaris: electrophysiology and anatomy of the neurons and their control by neuromodulators
Authors: Davis R. E. , Stretton A. O. W. 
Published: June 2009

SUMMARYAnalysis of the electrical properties of neurons in the motornervous system of Ascaris suum suggests that it is largely an analogue system. The motorneurons do not conduct action potentials and they release transmitter tonically at their normal resting potential; transmitter release is increased or decreased as a continuous function of membrane potential. Despite extensive physiological descriptions of the electrical properties of the neurons and their synapses, as well as morphological descriptions of the synaptic circuitry of the system, the predicted activities of the neurons in the circuit differ from those observed by direct recording in semi-intact behaving animals. We conclude that the description of the circuit is incomplete. There are several possibilities for the missing elements, including chemical, proprioceptive, and additional neuronal components. Recently, attention has been focussed most heavily on the intercellular chemical signalling systems; in addition to those mediated by classical neurotransmitters, a surprisingly complex array of neuropeptides has been identified. One family of these peptides, the AF peptides, has been analyzed in detail. It comprises at least 20 peptides, and they fall into sequence-related subfamilies. One of these subfamilies, containing 6 peptides, is encoded by a single transcript, suggesting that the AF peptides are under multiple genetic control. All AF peptides tested have potent activity on the motornervous system and or on muscle. There are multiple physiological activities, and cellular localization studies show multiple patterns of cellular expression. Studies on Panagrellus and Caenorhabditis emphasize the diversity of this family and its genetic control.
Pharmacology of anthelmintic resistance
Authors: Sangster N. 
Published: June 2009

SUMMARYAnthelmintic resistance has compromised the control of nematode parasites in several animal-based industries. Studies of resistance have not only improved our understanding of this phenomenon but also shed light on physiological systems of parasitic helminths. In addition, research on molecular aspects of anthelmintic resistance may provide selectable markers for use in future transfection studies with helminths. Several anthelmintics act on helminth neuromuscular systems. Drugs such as levamisole are cholinergic agonists and, based on pharmacological studies, levamisole-resistant nematodes appear to have altered acetylcholine receptors. It is likely that anticholinesterase anthelmintics share cross resistance with levamisole. Ivermectin appears to be a glutamate agonist.In vitrostudies of ivermectin-resistant nematodes suggest that IVM receptors are located on pharyngeal and somatic muscle. The free-living nematodeCaenorhabditis elegansmay provide a model for anthelmintic resistance. It has been useful in cloning drug receptors from parasites but differences between its life history and habitat compared with parasitic nematodes may limit its usefulness for studying resistance in these parasites.
Prospects for rational approaches to anthelmintic discovery
Authors: Thompson D. P. , Klein R. D. , Geary T. G. 
Published: June 2009

SUMMARYRational approaches to anthelmintic discovery include the design of screens for compounds directed at specific proteins in helminths that are pharmacologically distinguishable from their vertebrate homologues. The existence of several anthelmintics that selectively target the neuromusculature of helminths (e.g. levamisole, ivermectin, praziquantel, metrifonate), together with recent basic research in helminth physiology, have contributed to the recognition that neurobiology distinguishes these organisms from their vertebrate hosts. In this survey, we focus on mechanism-based screening and its application to anthelmintic discovery, with particular emphasis on targets in the neuromusculature of helminths. Few of these proteins have been exploited in chemotherapy. However, recent studies in comparative pharmacology and molecular biology, including theC. elegansgenome project, have provided insights on potential new targets and, in some cases, molecular probes useful for their incorporation in mechanism-based screens.