bluuebunny/crossref_metadata_2025_split huggingface dataset:
Density dependence in establishment, growth and worm fecundity in intestinal helminthiasis: the population biology ofTrichuris muris(Nematoda) infection in CBA/Ca mice
Authors: Michael E. , Bundy D. A. P. 
Published: June 2009

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

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

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

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

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

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

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

Three groups of lambs, aged 3, 5 and 6 months respectively, were infected daily with 5000 infective larvae of Trichostrongylus colubriformis for periods of 15–20 weeks. Some of the lambs also received a single challenge infection at the end of week 16. The course of the infections was monitored by means of faecal egg counts, measurement of live-weight gains and regular post mortem worm counts.There was an initial rapid increase in egg counts soon after patency, which was followed by an exponential fall in the counts in most lambs. This fall seemed to precede the expulsion of worms by a few weeks and was associated with reduced fecundity in the female worms. Furthermore, although the trend of the egg counts of some lambs suggested that a self-cure reaction had taken place, in a number of these lambs the low faecal egg counts did not reflect the size of their worm burden.Heavy worm burdens were usually associated with clinical symptoms of trichostrongylosis, including anorexia, diarrhoea and loss of weight. As the lambs developed resistance to reinfection and expelled their worm burden a rapid clinical recovery occurred, except in a few lambs which appeared to have suffered irreversible damage from the earlier heavy worm burden.The worm burden in most lambs appeared to be cumulative during the first 4–8 weeks before they developed a strong resistance to reinfection. There was considerable loss of the adult worm burden by 8–15 weeks after initial infection and some evidence of stunting in the remaining parasites.The immunological control of T. colubriformis infections in these lambs was achieved by means of the development of resistance to reinfection, inhibition of the ovulation of the female worms, stunting of adult worms and expulsion of adult worms by resistant lambs. These may be separate immune phenomena requiring different thresholds of parasitic material in individual animals, depending on their age, the rate and duration of infection and their innate ability to develop resistance to the parasite.
Antigenic variation duringTrypanosoma vivaxinfections of different host species
Authors: Barry J. D. 
Published: June 2009

SUMMARYThe sequence of appearance of specific lytic activity against more than 20 variable antigen types (VATs) ofTrypanosoma vivaxin the serum of 27 animals belonging to 5 species has been examined. For each host species there was a characteristic course of infection, with differences in height and duration of parasitaemia and in pathogenicity. The sequence of antigenic variation was similar in all host species, with some VATs consistently eliciting response more rapidly than others. The predominant group, comprising VATs which apparently developed within the first 3 weeks, varied in size according to the total number of trypanosomes in the bloodstream within that period, suggesting there is a spectrum, rather than discrete groupings, in the hierarchy of VAT expression. There was very little evidence for differences in appearance of VATs between host species; the only clear example was one VAT which apparently did not develop in one host species. The sequence of antigenic variation inT. vivaxseems to be determined by the parasite rather than the host species.
The regulation of malaria parasitaemia: parameter estimates for a population model
Authors: Gravenor M. B. , Mclean A. R. , Kwiatkowski D. 
Published: June 2009

SUMMARYClassical studies of non-immune individuals infected with Plasmodium falciparum reveal that the infection may be regulated for long periods at a relatively stable parasite density, despite the enormous growth potential of a parasite that continually replicates within host erythrocytes. This suggests that the parasite population may be controlled by density-dependent mechanisms, and in theory the most obvious of these is competition between parasites for host erythrocytes. Here we evaluate the role of this mechanism in the regulation of parasitaemia, by modelling the basic population interaction between parasites and erythrocytes in a form that allows all the essential parameters to be estimated from clinical data. Our results show that competition cannot account for the total regulation of P. falciparum, but when combined with immune mechanisms it may play a more important role than is generally supposed. Further analysis of the model indicates that in the long term, parasite replication at low parasite densities can contribute significantly to the high degree of anaemia observed in natural infection, a conclusion which is not obvious from simple clinical observation.
Differentiation between human and animal strains ofCryptosporidium parvumusing isoenzyme typing
Authors: Awad-El-Kariem F. M. , Robinson H. A. , Dyson D. A. , Evans D. , Wright S. , Fox M. T. , Mcdonald V. 
Published: June 2009

SUMMARYIsoenzyme typing was used to study a number of oocyst isolates ofCryptosporidium parvumfrom different geographical locations and of human or animal origin. All isolates showed identical enzyme motility when glucose phosphate isomerase (GPI; 23 isolates tested) or lactate dehydrogenases (LDH; 20 isolates tested) was assayed. However, two isoenzyme forms were observed with phosphoglucomutase (PGM; 9 animal isolates showed one form, while 8/9 human isolates showed a second form) and hexokinase (HK; 4 human isolates showed one form and 6 animal isolates showed a second form). Thus, PGM and HK each exhibit 2 isoenzymes corresponding to 2 parasite populations associated with separate hosts. The data from this study, plus supportive evidence obtained by different methods and by independent researchers, lend support to the hypothesis that separate cycles of transmission ofC. parvummay exist within human and animal hosts.
Analysis of antigen switching rates inTrypanosoma brucei
Authors: Lamont Gretel S. , Tucker R. S. , Cross G. A. M. 
Published: June 2009

SUMMARYPreviously quoted figures for the frequency of antigen switching inTrypanosoma bruceiare based on incorrect assumptions. In order to determine the correct switching frequency, an equation was derived that takes the growth rates of the newly expressed antigen types into consideration as well as the proportion of switched trypanosomes and the number of generations since the population was antigenically homogeneous. When this equation was applied to publishedin vitrodata, variable values were obtained for the switching frequency in clonal populations originally expressing one antigen type. The calculated most likely switching frequencies ranged from 1·4×10−7to 3·5×10−6. This variation was probably caused by differences in the growth rates of the new antigen types in the population and failure to detect slow growing variants. To overcome these problems, an experimental procedure was developed to analyse the switching frequencyin vitro. Trypanosomes were cloned and grown in parallel cultures. After an appropriate number of generations, cells expressing the original antigen type were destroyed and, from the proportion of cultures that contained new antigen types, the switching frequency was calculated. The technique minimized subculturing or other procedures that could distort the results. Although the method was optimized for analysing switching frequency, the values differed between experiments, ranging from 2·2×10−7to 2·6×10−6for one variant. Possible causes for the variations in switching frequency are discussed.
The role of serum in leucocyte adherence to the plerocercoid ofLigula intestinalis(Cestoda: Pseudophyllidea)
Authors: Hoole P. , Arme C. 
Published: June 2009

SUMMARYThe role of serum in the adherence of roach (Rutilus rutilus) leucocytes to the plerocercoid ofLigula intestinalishas been investigatedin vitro. Roach plerocercoids, either untreated, cultured or killed (fixation in 0·5 % buffered glutaraldehyde or heat at 50°C for 45 mm), were exposed to serum and 4×106leucocytes obtained from the pronephros of non-infected roach using a discontinuous Percoll gradient. At normal roach serum (NRoS) dilutions of 1:5000 to 1:100, leucocyte adherence was observed on all living parasites but was negligible in killed parasites or in complement-depleted NRoS assays. The number of adherent cells increased with increasing NRoS concentration. Leucocytes bound more avidly in the presence of heat-inactivated immune serum (hi IRoS); at a serum dilution of 1:5000 the percentage of the parasite surface covered by leucocytes was approximately 3 times greater in hi IRoS than in NRoS. Ultrastructural observations on parasites revealed that plerocercoids exposed to cells and hi IRoS had, in some areas, abnormal inclusions in their tegument and lacked a microthrix border and distal cytoplasm. In addition, the efflux of radioactivity from [14C] cycloleucine-labelled worms was greater in parasites incubated in the presence of hi IRos.
The relationship between worm burden and levels of a circulating antigen (CAA) of five species ofSchistosomain mice
Authors: Agnew A. , Fulford A. J. C. , De Jonge N. , Krijger F. W. , Rodriguez-Chacon M. , Gutsmann V. , Deelder A. M. 
Published: June 2009

SUMMARYThis study examines the ability of an assay which measures the amount of a schistosome specific antigen (CAA) in the host circulation to reliably reflect relative worm burden. Mice were infected with 5 species of schistosome with a range of infection dose. The levels of serum CAA increased during schistosome maturation. In all species tested CAA levels correlated well with adult worm burden once the parasites achieved sexual maturity and remained relatively stable during the establishment of egg production. The amount of CAA produced varied between species but within each species CAA levels were proportional to worm numbers: no density-dependent effects on CAA levels were observed even when mice carried worm burdens that were very large relative to host size. T-cell deprivation of the host had no effect on the CAA/worm burden relationship in eitherSchistosoma mansoniorS. haematobiuminfections and the CAA equilibrium was unaltered in intact mice when reduction of worm fecundity occurred. These data support the use of the CAA as an accurate and robust estimate of relative schistosome burden in man.
The effects of age, temperature and shadow stimuli on activity patterns of the cercariae of Cryptocotyle lingua (Digenea: Heterophyidae)
Authors: Rea J. G. , Irwin S. W. B. 
Published: June 2009

SUMMARYThe behaviour of cercariae was recorded on video at 10, 20 and 30 °C and a combination of population and individual behavioural patterns studied. Initially cercarial populations were extremely active, individuals alternating between swimming and sinking behaviour. As they aged the percentage sinking and resting increased resulting in the establishment of a vertical distribution in the water column. An increased environmental temperature reduced the active life-span of the parasites. Over time cercarial swimming rates declined. Swimming rates increased with environmental temperature and as a result of a shadow stimulus. As cercariae aged, the duration of swimming events decreased. Post-stimulation swimming periods were significantly longer than pre-stimulation periods. Pre- and post-stimulation swimming distances also declined with age. Post-stimulation swimming distances were significantly longer than pre-stimulation distances. The sinking rates of cercariae decreased with age while sinking periods and distances increased. Data for proportional time spent swimming and the ratio of sinking to swimming events indicated that as cercariae aged, less time was spent swimming. The frequency of swimming/sinking events declined with age. The implications of this behaviour for dispersal and transmission are discussed.
Comparative analyses of the neuropeptide F (NPF)- and FMRFamide-related peptide (FaRP)-immunoreactivities in Fasciola hepatica and Schistosoma spp
Authors: Marks N. J. , Halton D. W. , Maule A. G. , Brennan G. P. , Shaw C. , Southgate V. R. , Johnston C. F. 
Published: June 2009

SUMMARYImmunochemical techniques were used to determine the distribution, chemical characteristics and relative abundance of immunoreactivity (IR) to two native platyhelminth neuropeptides, neuropeptide F (NPF) (Moniezia expansa) and the FMRFamide-related peptide (FaRP), GNFFRFamide, in the trematodes, Fasciola hepatica and Schistosoma mansoni; the larger S. margrebowiei was used in the chemical analysis. Extensive immunostaining for the two peptides was demonstrated throughout the nervous systems of both F. hepatica and S. mansoni, with strong IR also in the innervation of muscular structures, including those associated with the egg-forming apparatus. The patterns of immunostaining were similar to those previously described for the vertebrate neuropeptide Y superfamily of peptides and for FMRFamide. Ultra-structurally, gold labelling of NPF- and GNFFRFamide-IRs was localized exclusively to the contents of secretory vesicles in the axons and somatic cytoplasm of neurones. Double-labelling experiments showed an apparent homogeneity of antigenic sites, in all probability due to the demonstrated cross-reactivity of the FaRP antiserum with NPF. Radio-immunoassay of acid-ethanol extracts of the worms detected 8·3 pmol/g and 4·7 pmol/g equivalents of NPF- and FMRFamide-IRs, respectively, for F. hepatica, and corresponding values of 4·9 pmol/g and 4·3 pmol/g equivalents for S. margrebowiei. Gel-permeation chromatography resolved IR to both peptides in discrete peaks and these eluted in similar positions to synthetic NPF (M. expansa) and GNFFRFamide, respectively.