bluuebunny/crossref_metadata_2025_split huggingface dataset:
Response of Haemonchus contortus cayugensis to a change in the ratio of smooth to linguiform
Authors: Jambre L. F. Le , Ractliffe L. H. 
Published: June 2009

The equilibrium, of vulvar phenotypes in Haemonchus contortus cayugensis was changed by infecting lambs with either a selected strain of smooth or of linguiform worms. Subsequently the lambs grazed the same pasture and observations were made on changes in worm populations in the lambs, and on pasture it appeared that the seasonal change in the relative frequencies of A and B linguiform worms was related to density-dependent factors in the host. In the spring, when lambs first become infected, the worm population is small and the majority of linguiform worms are A-type. As the season progresses the density of the parasite population increases. Once the population becomes crowded selection begins to favour the B-type females. The effects of crowding on linguiform A females can be seen as a positive correlation between the percentage of linguiform A and their weight. Population density also affected the survival of A-type worms since there was a negative correlation of percentage A-type on total worm numbers. There was a similar negative correlation between percentage A-type and total worm numbers in both the continuously infected and tracer lambs.Population density did not affect the proportion of smooth worms. However, smooth worms increased in the tracers from, approximately 10% at the beginning of the experiment to 55% at its conclusion 18 weeks later. The latter percentage is almost within range of the local subspecies, which has 60% or more smooth worms. It appears therefore that the proportion of smooth to linguiform worms is a stable equilibrium maintained by natural selection.
Dipetalonema viteae in hamsters: effect of antiserum or immunization with parasite extracts on production of microfilariae
Authors: Haque A. , Lefebvre M. N. , Ogilvie B. M. , Capron A. 
Published: June 2009

SummaryAfter hamsters have been infected with Dipetalonema viteae for about 4 months, microfilariae disappear from the circulation but the adult worms remain alive and active. Such hamsters are said to harbour a ‘latent’ infection. Additional adult worms implanted into such hamsters produce no microfilariae, but adult worms recovered from hamsters with latent infections resume microfilariae production when surgically transplanted into new hosts. In vitro, worms from hamsters with latent infections renewed microfilariae production in the presence of serum from uninfected but not infected hamsters. Serum from infected animals had a marked suppressive effect on the microfilariae production of adult worms implanted into passively immunized hamsters. This suggests that microfilarial release is regulated by a serum factor. Microfilarial production in in vitro and in vivo experiments was more strongly inhibited by serum taken from hamsters with latent infections and hamsters infected for only 30 days (pre-patent) than by serum taken 90 days after infection (whilst microfilariae were in the circulation of the serum donors). A cytotoxic effect of sera from infected hamsters on the microfilariae could not be demonstrated.In animals immunized by extracts of adult worms or microfilariae, microfilaraemia was considerably reduced. In contrast, animals immunized repeatedly with the extract from small numbers of microfilariae during the pre-patent phase of an infection had an enhanced microfilaraemia. Adult worm numbers were not affected by immunization except in animals given extract from a single female worm which harboured fewer worms than controls.
The effect of variations in host and parasite density on the level of parasitization of Lymnaea truncatula by Fasciola hepatica
Authors: Wilson R. A. , Taylor Susan L. 
Published: June 2009

SummaryGroups of the snail Lymnaea truncatula, maintained at a range of spatial densities, were exposed to different densities of miracidia of Fasciola hepatica. The resulting degree of parasitization was measured 3–4 weeks after infection. The relationship between parasite densities and parasitization appeared to be curvilinear. The lower than expected parasitization at high parasite densities could be explained by the multiple infection of some snails by two or more miracidia.The level of parasitization was not related exponentially to the temperature at which infection was carried out. This was thought to be due to the inverse relationship between miracidial longevity and swimming speed, with respect to temperature. A depth of free water overlying a mud surface was an absolute requirement for miracidia to successfully infect snails.
Studies on the transmission and course of infection of a Kenyan strain of Theileria mutans
Authors: Young A. S. , Purnell R. E. , Payne R. C. , Brown C. G. D. , Kanhai G. K. 
Published: June 2009

SummaryTheileria mutans (Aitong) isolated from cattle exposed in the Narok District of Kenya and blood-passaged through cattle 8 times, appeared to have lost its original pathogenicity for cattle. It was demonstrated that the parasite was trans-stadially transmissible by the tick Amblyomma variegatum but not by Rhipicephalus appendiculatus. Four tick–bovine passages were made using A. variegatum, and infective parasites were also harvested from A. variegatum nymphs which had been fed for 5 days on rabbits. Blood containing piroplasms, or lymphoid cells infected with schizonts taken from cattle, at the 2nd tick–bovine passage were shown to be infective on inoculation.The course of the T. mutans infections in the cattle was studied. In tick-induced infections macroschizonts occurred transiently, persisting longest in circulating lymphoid cells. Microschizonts were rarely detected. The macroschizonts were morphologically distinct from those of other Theileria species described from East Africa.In tick-induced infections, the piroplasm parasitaemia increased rapidly and there was evidence of restored pathogenicity of the parasite since high piroplasm parasitaemias were associated with a marked anaemia.
Schistosoma mansoni: a comparative study of artificially transformed schistosomula and schistomula recoverd after cercarial penetration of isolated skin
Authors: Brink Linda H. , McLaren Diane J. , Smithers S. R. 
Published: June 2009

A comparison was made of the ultrastructure, development and antigenic nature of the surfaces and of the viability of three types of schistosomula ofSchistosoma mansoni: schistosomula formed afrer cercariae had penetrated isolated skin (SS), schistosomula produced after mechanical separation of cercarial tails from bodies (MS), and schistosomula transformed from cercariae after incubation in fresh rat serum (RS).Within 2 h of transformation, the surface membrane of all three types of schistosomula had changed from trilaminate to heptalaminate structures and SS and MS had lost their cercarial glycocalyx. Initially a dense amorphous material was demonstrated on the surfaces of RS, which was thought to be the result of an interaction between a factor in rat serum and the glycocalyx: this material was greatly reduced within 2 h of transformation. The pre-acetabular glands of SS were emptied while those of MS and RS retained their contents. Immunofluorescent studies showed that all schistosomula bound serum from mice immune toS. mansoni, but the binding was stronger with MS and RS. The mixed agglutination reaction demonstrated the presence of human A and B blood group-like antigenic determinants on approximately 30% of 3 h old SS; these determinants were not detected on MS or RS.In vitro, the development of MS and RS was similar to SS; the first schistosomula reached the ‘gut-closed’ stage by day 10; 50–70% of SS reached this stage by day 12, in contrast to only 25–50% of MS and RS. Between 28 and 45% of all schistosomula developed to maturity when injected intravenously into mice.It was concluded that the two types of artificially prepared schistosomula fultil the main criteria of transformation from cercaria to schistosomulum. Further, it is suggested that MS are the most appropriate source of material for immunochemical and physiological studies.
The longevity of Hymeonlepis microstoma in mice, and its immunological cross-reaction with Hymenolepis diminuta
Authors: Hopkins C. A. , Goodall R. I. , Zajac A. 
Published: June 2009

Hymenolepis microstoma was found to live for at least 728 days in a mouse, but an initial infection of 10 worms per mosue decreased exponentially for approximately the first 110 days to a level of 3–5 worms, after which little further loss occurred.A primary infection of six H. microstoma, expelled with anthelmintic on day 21, strongly protected against a single worm H. diminuta challenge; worms in 80 ‘immunized’ mice weighed less than 5% of the weight of worms from 80 control mice. However, a primary (5-worm) H. diminuta infection led only to a small, though statistically significant, decrease in weight of the 3-worm H. microstoma challenge.The results are interpreted as indicating that H. microstoma evokes a strong immunological response which cross-reacts with H. diminuta. The failure of H. diminutato protect strongly against a 3-worm challenge by H. microstoma suggests, as does the long survival of a primary infection when it is reduced to approximately 4 worms, that H. microstoma survives in low infection because it is able to avoid the immune response. This could be due to antigen camounflage, ability to repair immune damage or to the low permeability of the bile duct wall to components of the immune response. The worm loss which occurs from heavy infection until only 3–5 worms remain may be physiologically rather than immunologiacally mediated.
Early developmental changes of the schistosomula ofSchistosoma mansoni in vitroand in mouse lung
Authors: Imohiosen E. A. E. , Sher Alan , Lichtenberg F. Von 
Published: June 2009

SummaryFresh (3 h) schistosomula ofSchistosoma mansoniwere obtained by the skin penetration method and injected intravenously into groups of mice either immediately or after 48 h incubation in tissue culture. Schistosomula were then recovered from the lungs 1 to 2 days after injection. The recovery results showed that the ability of uncultured schistosomula to emerge from lung tissue increased with time, became maximal on the 3rd day and diminished thereafter. In contrast, cultured schistosomula were able to emerge from chopped lung at a much earlier time after injection.Fresh schistosomula, as well as those recovered from mouse lungs, were assayed by indirect immunofluorescence for the presence of parasite and host antigens. Similarly, fresh schistosomula which had been incubated in foetal calf serum, with or without mouse red blood cells, were assayed for parasite and host antigens after 3–24 h of culture. Fresh schistosomula expressed parasite antigen with greater intensity than those recovered from mouse lungs and showed no trace of host antigen. Lung schistosomula, on the other hand, expressed less parasite antigen but more red blood cell antigen with increasing time in the host. Schistosomula cultured in the absence of mouse red blood cells expressed only parasite antigen throughout the period in culture, while those cultured in the presence of mouse red blood cells also expressed parasite antigen during the entire period in culture but, in addition, by 24 h host antigen could also be detected.These developmental and adaptational changes may play a role in determining the survival of parasites in the normal or immune host.
Corynebacterium parvumas an adjuvant forTrypanosoma cruziepimastigote vaccines: a comparison with saponin andBordetella pertussis
Authors: Bomford R. , McHardy N. 
Published: June 2009

SUMMARYThe effect was compared in CBA mice of addingCorynebacterium parvum, saponin, andBordetella pertussisto living or killedTrypanosoma cruzi(Y strain) epimastigote vaccines on the induction of protective immunity against subcutaneous (s.c.) challenge with blood trypomastigotes. The addition ofC. parvumto a low dose ofT. cruzivaccine, which alone was non-protective, generated a greater degree of protection than did saponin orB. pertussis. C. parvumalone increased resistance to infection to a variable and usually weak extent. The addition ofC. parvumto larger doses ofT. cruzivaccine, which were themselves sufficient to elicit some degree of protection, improved resistance when the challenge was given 1 or 12 weeks after immunization, but lowered it at 3 weeks. It is concluded that the comparative efficacy of adjuvants forT. cruzivaccines needs to be assessed on 3 parameters: (1) the dose of antigen, (2) the dose of adjuvant and (3) the time interval between immunization and challenge.
Patterns of milk transmission of Strongyloides ratti
Authors: Wilson P. A. G. , Cameron Maureen , Scott D. S. 
Published: June 2009

SummaryEight days after mother rats were injected with 4000 infective larvae of Strongyloides ratti at different stages of lactation the numbers of adult worms in their intestines were uniformly low (< 3% of the dose) compared with unmated controls (mean = 25%). Those in their litters varied from 12% on day 5 to a maximum of 47% on day 17 post partum. These data, which do not correlate with lactational performance, imply that parasite movements in lactating rats are controlled by qualitative, not quantitative, consequences of humoral events. The numbers of worms in litters are concluded to be the result of the interaction of dynamic determinants of larval routes in the mother and changes in the suitability of the neonatal gut as an environment for worm development. The timing of events leading to milk-borne infection is defined. Injected larvae were closely synchronized in their movements, which were completed in 36 h. Larvae experimentally diverted into the mother's tissues during her first lactation were not available for the infection of a second litter.
Population dynamics of snail infection by miracidia
Authors: Anderson R. M. 
Published: June 2009

SummaryThe essential biological features of snail infection by miracidia are incorporated into a simple model which describes the rate of change with respect to time of the number of miracidial infections/host. The model is based on the assumption that the net rate of infection is directly proportional to the density of both miracidia and hosts. Empirical evidence is provided to support this assumption. The basic framework of the model is expanded to take into account demographic stochasticity in infection and is used to predict the percentage of snails that become infected after exposure to a known number of miracidia for a set period of time. The influence of miracidial mortalities and age-dependent infectivity are examined and theoretical predictions are compared with a range of experimental results.Underlying heterogeneity in the distribution of the number of infections/snail is shown to generate an artifactual decrease in infection rates as exposure density rises, if rate estimation procedures are based on an assumption of randomness. Empirical evidence is presented to illustrate the generation of over-dispersion in the number of miracidial infections/snail under tightly controlled laboratory conditions, using supposedly homogeneous snail populations.Biological causes for underlying patterns of heterogeneity are discussed in relation to snail susceptibility to infection and ‘attractiveness’ to infective stages.
The cestocidal effect of complement in normal and immune sera in vitro
Authors: Herd E. P. 
Published: June 2009

SummaryThe effects of complement and/or specific antibodies on the larval and adult stages of Echinococcus granulosus were studied in vitro. Lysis and death of both protoscoleces and adult E. granulosus occurred within 10 min to 24 h in 50% fresh normal sera used as a source of complement, without the presence of specific antibodies. The lytic and lethal reaction was marked in fresh sera from guinea-pigs, calves, dogs, man and sheep, but only slight in fresh sera from English rabbits and horses. Guinea-pig sera were shown to be complement deficient after reacting with worms and all reactions were abolished after sera had been heated to 56 °C for 30 min. Fluorescent antibody studies failed to detect host antibodies at the parasite tegument. It is suggested that activation of the complement system occurs via the alternate pathway, that it acts independently of the immune system and that it is lethal to a wide range of cestode parasites.In contrast, marked agglutination/precipitation reactions with protoscoleces and precipitation reactions with adult E. granulosus were observed after incubation in heat inactivated 50% canine antisera, but not in normal sera. The antigen-antibody nature of these reactions was established by fluorescent antibody studies and the areas of antibody attack pinpointed. In spite of these reactions, worms remained healthy and active over a period of 8 days.
Separation of Isospora (Toxoplasma) gondii cysts and cystozoites from mouse brain tissue by continuous density - gradient centrifugation
Authors: Cornelissen A. W. C. A. , Overdulve J. P. , Hoenderboom J. M. 
Published: June 2009

SUMMARYA simple, quick and reproducible method consisting of density-gradient centrifugation of homogenized infected mouse brain tissue on Percoll is described for the isolation and purification of cysts of Isospora (Toxoplasma) gondii. A 100% recovery of cysts, with 74·2% in a single fraction with a specific gravity of 1·056, was obtained by overlaying homogenates of infected mouse brains on a pre-formed Percoll gradient and centrifugation at low g forces. With this procedure recovery was independent of the age of the cysts. Titration of purified cystozoites showed there to be no loss of infectivity.
Isolation and partial characterization of the tegumental outer membrane of adultSchistosoma mansoni
Authors: Simpson A. J. G. , Schryer M. D. , Cesari I. M. , Evans W. H. , Smithers S. R. 
Published: June 2009

SUMMARYIncubation of adultSchistosoma mansoniat 37 °C in chemically defined media caused the shedding of variable amounts of the parasite's tegument. In phosphate-buffered saline, pH 7·4, 37% of125I-labelled wheat germ agglutinin which was attached to the schistosome surface was released within 5 min. When the released material was collected by centrifugation at 55000gfor 1 h, the pellet was seen to consist of components of the parasite tegument and contained 1% of the parasite protein and 6·2% of the 5′-AMPase activity. By monitoring the release of the gut enzyme, haemoglobinase, it was shown that predominantly tegumental material was released under these conditions. The material released from the parasite was separated by discontinuous sucrose gradient centrifugation into 4 major fractions and it was shown that a material banding at low density was highly enriched in vesicles of parasite outer membrane. Major polypeptides of apparent molecular weights 135000, 110000, 90000, 65000, 47000 and 40000 and glycoproteins of apparent molecular weights 135000, 120000, 65000, 63000 and 30–40000 were identified in this fraction. Comparison of the distribution of 5′-AMPase activity and the contents of each fraction as revealed by ultrastructural examination showed that this enzyme is a good marker for the tegumental outer membrane.
The ribosomes of Plasmodium berghei: isolation and ribosomal ribonucleic acid analysis
Authors: Miller F. W. , Ilan Judith 
Published: June 2009

SummaryRibosomes and high molecular weight ribosomal ribonucleic acid (rRNA) from the blood stages of Plasmodium berghei parasites were studied in preparations free from host ribosome contamination. Purified malarial ribosomes were isolated in high yield from a population of ultrastructurally intact, viable parasites by hypertonic lysis with Triton X-100 and differential centrifugation. These ribosomes were shown to be derived from active polysomes and could be dissociated into subunits by puromycin–0·5 m KCl treatment. Malarial rRNA extracted from purified 40S and 60S ribosomal subunits was characterized by electrophoretic, sedimentation and base ratio analyses. Like certain other protozoa, the P. berghei 40S ribosomal subunit possessed an exceptionally large RNA species (mol. wt 0·9 × 106), while RNA isolated from the parasite's 60S subunit (mol. wt 1·5 × 106) was specifically ‘nicked’ to produce one large component (mol.wt 1·2 × 106) and one small component (mol.wt 0·3 × 106) in equimolar quantities. These rRNA's migrate identically on polyacrylamide gels after heating to 63°C for 5 mm or under denaturing conditions in the presence of formamide, indicating an absence of aggregation and non-specific degradation of the rRNA species. Base composition studies showed P. berghei rRNA to be low in guanosine and cytosine content, as is the case for protozoa generally.
Invasion of vertebrate lungs by the polystomatid monogeneans Pseudodiplorchis americanus and Neodiplorchis scaphiopodis
Authors: Tinsley R. C. , Earle Celia M. 
Published: June 2009

SUMMARYSome unique features of monogenean biology have emerged from studies on 2 polystomatids which infect spadefoot toads in Arizona, USA: Pseudodiplorchis americanus in Scaphiopus couchii and Neodiplorchis scaphiopodis in S. multiplicatus and S. bombifrons. Transmission is confined to 1–3 nights each summer when the desert-adapted toads enter water to spawn. Encapsulated larvae complete development in utero and hatch within seconds of deposition; their body length (up to 600 μm) is 2–4 times greater than that of most other oncomiracidia, and their swimming life (over 48 h at 25–27 °C) is twice that usual amongst monogeneans. The ciliated oncomiracidia invade the nostrils, a target usually above the water surface and requiring migration over the exposed skin; remarkably they tolerate drying for up to 1 h (at 32 °C, 45% rel. hum.). The larvae migrate via the buccal cavity and glottis to the lungs where juvenile development occurs until early autumn. Migration from the lungs to the urinary bladder (by an as yet undetermined route) is followed by maturation and reproduction during host hibernation, and developing embryos accumulate in preparation for a period of transmission more restricted than that of any other monogenean. No other monogenean is known to exploit the lungs nor to inhabit, successively, anterior and posterior sites of the same adult host individual.
The production and functional morphology of helminth egg-shells
Authors: Wharton D.A. 
Published: June 2009

SUMMARYThe high energy costs of egg-shell production in many helminths suggests that this structure plays an important role in their biology. The mechanical and chemical resistance of the egg-shell and the barrier it provides to the entry and loss of material are important in the survival of the free-living stages within the egg. The presence of egg filaments may increase the availability of infective stages and the operculum may be important in the infective process.
Plasmodium berghei-infected red cells sorted according to DNA content
Authors: Howard R. J. , Battye F. L. 
Published: June 2009

SUMMARYA cell-sorting method is described for the analysis and separation of red blood cells in Plasmodium berghei-infected mouse blood based on their DNA content. This method involves a selective uptake of the bis-benzimidazole dye 33258 Hoechst, a DNA-binding dye, by red blood cells containing parasites. Infected blood is incubated at 37 °C with the dye then washed at 4 °C to remove unbound dye. Uninfected cells are then non-fluorescent at the characteristic wavelengths for 33258 Hoechst excitation and emission, whereas parasitized cells display fluorescence intensities in approximately direct proportion to the number of parasite nuclei (i.e. amount of parasite DNA) within the cell and can be sorted accordingly. Providing cells were incubated in a complex nutrient medium during dye uptake at 37°C, the sorted parasite cells produced lethal P. berghei infections when injected into BALB/c mice. The dyelabelling technique is simple and sufficient red blood cells at various stages of infection can be collected for biochemical or immunochemical studies by cell sorting.