bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparative analysis of thePlasmodium falciparumhistidine-rich proteins HRP-I, HRP-II and HRP-III in malaria parasites of diverse origin
Authors: Rock E. P. , Marsh K. , Saul A. J. , Wellems T. E. , Taylor Diane W. , Maloy W. L. , Howard R. J. 
Published: June 2009

SUMMARYPlasmodium falciparum-infectederythrocytes (IRBC) synthesize 3 histidine-rich proteins: HRP-I or the knob-associated HRP, HRP-II and HRP-III or SHARP. In order to distinguish these proteins immunochemically we prepared monoclonal antibodies which react with HRP-I, HRP-II and HRP-III, and rabbit antisera against synthetic peptides derived from the HRP-II and HRP-III sequences. A comparative analysis of diverseP. falciparumparasites was made using these antibodies and immunoprecipitation or Western blotting. HRP-I(Mr80000–115000) was identified in all knob-positiveP. falciparumparasites including isolates examined directly from Gambian patients. However, this protein was of lower abundance in these isolates and in 6 knob-positive, culture-adapted parasites compared toAotusmonkey-adapted parasites or culture-adapted parasites studied previously. HRP-II(Mr60000–105000) was identified in allP. falciparumparasites regardless of knob-phenotype, and was recovered from culture supernatants as a secreted water-soluble protein. Within IRBC, HRP-II was found as a complex of several closely spaced bands. Cell surface radio-iodination of IRBC from several isolates and immunoprecipitation with a rabbit antiserum against the HRP-II repeat sequence identified HRP-II as a surface-exposed protein. Like HRP-I, the abundance of HRP-II was lower in the Gambian isolates than withAotusmonkey-adapted parasites studied earlier. Neither HRP-I nor HRP-II were identified in a knob-positive isolate ofP. malariaecollected from a Gambian patient. Analogues of these HRP were also absent from asexual parasites of diverse primate and murine malaria species screened with this panel of antibodies. HRP-III(Mr40000–55000) was distinguished by its lower apparent size and by specific reaction with rabbit antibody against its 5-mer repeat sequence. HRP-III was of lowest abundance compared with the other two HRP. These antibody reagents and distinguishing properties should prove useful in studies on the separate functions of the 3P. falciparumHRP.
Scanning electron microscopy of the tegument of adult S. margrebowiei Le Roux, 1933 with particular reference to the structure of the tubercles
Authors: Probert A. J. , Awad A. H. H. 
Published: June 2009

SUMMARYThe tegumental surface of Schistosoma margrebowiei as viewed by scanning electron microscopy is described. Both spined and unspined tubercles were found on the dorsal and dorso-lateral surfaces of sexually mature (in copula) male worms. Unpaired males lacked spined tubercles and the development of the spines is considered to occur only when worms are in copula. The females lack tubercles. The importance of tubercle structure in the identification of schistosome species and the effect of sexual maturity on their development is discussed.
The application of control analysis to helminth pathways
Authors: Barrett J. 
Published: June 2009

SummaryParasitic helminths have an absolute requirement for carbohydrate for their energy metabolism, there being no significant contribution from fatty acid or amino acid catabolism. There is no significant synthesis of glucose or glycogen from non-hexose precursors in helminths and so they are dependent on dietary carbohydrate. Characteristically parasitic helminths break down glycogen or glucose via linear anaerobic pathways to give reduced organic end-products, usually acids such as lactate, acetate, succinate and propionate or more rarely alcohols such as ethanol, propanol and acetoin (Barrett, 1984).
Hybrids between Schistosoma mansoni and S. rodhaini: characterization by cercarial emergence rhythms
Authors: Thèron A. 
Published: June 2009

SummaryHybridization between Schistosoma mansoni, with a diurnal cercarial emergence rhythm and S. rodhaini, with a nocturnal cercarial shedding pattern leads to F1 and F2 generations, hybrid schistosomes whose chronobiological phenotype of cercariae is characterized by two unequal emergence peaks, one diurnal and the other nocturnal. The relative importance of diurnal and nocturnal peaks depends upon which S. mansoni strain (early or late) is used for the hybridization with S. rodhaini. The results are compared and discussed with those resulting from crosses between intraspecific sympatric and allopatric chronobiological variants (early and late) of S. mansoni. The genetic determinism of the cercarial emergence of schistosomes and the significant differences observed between cercarial shedding patterns of parental species and their hybrids allow the use of this behavioural marker in biological and genetical studies in schistosome populations.
The weight/length profiles of Ascaris lumbricoides within a human community before mass treatment and following reinfection
Authors: Elkins D. B. , Haswell-Elkins M. 
Published: June 2009

SummaryWeight and length profiles are presented of 3505 Ascaris worms recovered after mass anthelmintic treatment of a human community in January 1984 and, after an 11 month period of reinfection, in November 1984. Male and female worms recovered after reinfection were significantly heavier and longer than those expelled after initial treatment (P < 0·0001). Multiple regression models were employed to examine variability in parasite size. A positive influence of host body weight on the weight of parasites recovered in January, but not in November, was observed. No negative relationship was recorded at either date between worm size and the total number of worms harboured, even after controlling for host weight. Striking host age-related variability was observed in the distribution profile of weights and lengths of individual worms recovered in January. Children harboured predominantly smaller worms before initial treatment, while adults expelled mainly heavy worms. In contrast, worms expelled by both children and adults after reinfection were heavier and more homogeneous in size, particularly within the relatively heavily infected group. These patterns argue against a primary role for density- dependent or acquired resistance mechanisms in determining the size of Ascaris in humans. However, the results are consistent with a hypothesis initially suggested by Jung (1954) that established worms may inhibit the development of newly acquired Ascaris larvae, perhaps regulating their own abundance.
The formation of the first-stage cuticle within the egg of Trichostrongylus colubriformis
Authors: Wharton D. A. , Bone L. W. 
Published: June 2009

SummaryThe ultrastructure of the formation of the first-stage cuticle within the egg of Trichostrongylus colubriformis is described. The first indication of cuticle formation was the formation of the epicuticle external to the epidermal plasma membrane. This becomes thickened to form the epicuticle of the fully formed cuticle. Microtubules and microfilaments associated with the epidermal plasma membrane were observed during the early phases of cuticle formation. The basal zone was secreted into the space between the epicuticle and the epidermal plasma membrane, followed by the formation of the cortical zone. The basal zone had a striated appearance during the earliest stages of its formation.
The effect of drugs on the cell cycle ofGiardia intestinalis
Authors: Hoyne G. F. , Boreham P. F.L. , Parsons P. G. , Ward C. , Biggs B. 
Published: June 2009

SummaryFlow cytometric analysis of the binucleated protozoan parasiteGiardia intestinalisgave DNA histograms with a broad Gl peak and a definable G2 + M peak with twice the DNA content of Gl. Twenty-four hour treatment with metronidazole arrested cell cycle progression of susceptible trophozoites in the G2 + M phase, but had no effect, even at toxic doses, on the DNA histogram of a line selected for resistance to metronidazole. Furazolidone was inhibitory to both stocks, causing an arrest in the S and G2 + M phases. Inhibitors of the mammalian cell cycle were also tested. Hydroxyurea, which blocks mammalian cells in Gl/S, and razoxane, which blocks in G2 + M, arrested trophozoites in the G2 + M phase whereas colchicine and gamma-irradiation had little or no effect on the cell cycle ofG. intestinalis. These results suggest that the cell cycle ofG. intestinalismay be controlled in a different manner from mammalian cells.
Differentiation of Schistosoma mansoni from S. rodhaini using cloned DNA probes
Authors: Walker Tina K. , Simpson A. J. G. , Rollinson D. 
Published: June 2009

SummaryThe ribosomal RNA (rRNA) gene units of Schistosoma mansoni and S. rodhaini, of the lateral spined egg group, have been studied. The schistosome rRNA gene unit consists of a regular interspersion of the two genes encoding the large and small rRNA units with two spacers. The large spacer is not transcribed while the small spacer is part of the transcription unit. Variation in the rRNA gene unit between the two species is demonstrated to take the form of loss or gain of restriction sites within the non-transcribed and transcribed spacers. This variation has been demonstrated to enable the differentiation of S. mansoni from S. rodhaini by Southern hybridization analysis. In addition, a DNA clone representing a female specific, tandemly repeated sequence, is demonstrated to enable differentiation of S. mansoni and S. rodhaini using dot blot hybridization analysis.
Antigenic relatedness of stocks and clones ofTrypanosoma vivaxfrom East and West Africa
Authors: Vos G. J. , Gardiner P. R. 
Published: June 2009

SummaryThe antigenic relationships of 7 stocks and 7 clones ofTrypanosoma vivaxfrom East and West Africa were compared by immune lysis. Sera from goats infected with different stocks and clones ofT. vivax, collected on days 40 and 80 after infection, were used in the immune lysis test with homologous and heterologous stocks and clones of trypanosomes. Sera from infected cattle were included to compare stocks and clones from Kenya. The parasites that were used as antigen in the immune lysis tests were collected from infected mice when variable antigen type (VAT) homogeneous populations were used, from goats for infection with stocks and clones from Nigeria, The Gambia and Uganda, and from cattle for Kenyan stocks. Reciprocal cross-reactivity between sera and parasites was found between all the stocks and clones from Nigeria and The Gambia with the exception of one clone from Nigeria that was not recognized by antisera to a clone from The Gambia. There was also cross-reactivity between a stock and clone from Uganda and stocks and clones from Nigeria and The Gambia. Sera from goats infected with stocks and clones from Nigeria, The Gambia and Uganda recognized parasite populations that were homogeneous for one VAT (ILDat 1.2) of the rodent infective stock from Nigeria. Some antisera to West African stocks recognized another stable variant from a Ugandan stock adapted to rodents (ILDat 2.1), indicating that these VATs were expressed in the repertoires of the heterologous stocks. There was no cross-reaction between stocks from Nigeria, The Gambia or Uganda with Kenyan stocks. A stock from Galana (Kenya) and Bamburi (Kenya) showed reciprocal cross-reactivity. Two other Kenyan stocks, from Kilifi and Likoni, also showed cross-reactivity by immune lysis but showed no antigenic relationship with the other Kenyan stocks.
Factors affecting the intensity of reinfection with Schistosoma haematobium following treatment with praziquantel
Authors: Chandiwana S. K. , Woolhouse M. E. J. , Bradley M. 
Published: June 2009

SUMMARYInfection with Schistosoma haematobium was studied in a rural community of approximately 500 persons in eastern Zimbabwe. The overall prevalence of infection, as determined by urine egg counts, was 40·1%, and of heavy infections (≥ 50 eggs/10 ml urine) was 11·0%. The prevalence of both heavy and all infections was highest in the 8 to 10-year-old age class. During 1987–88 data were obtained from 102 individuals on intensity of reinfection 14 weeks after treatment with praziquantel, the efficacy of treatment having been determined after 4 weeks. The water contact made by these individuals during 2-week periods immediately following treatment was recorded. The relative abundance of patent infected intermediate host snails, Bulinus globosus, was also monitored. An index of exposure was developed which weighted each water contact by its duration, the type of activity, the time of day, and the abundance of infected snails at the site used. The relationships between rates of reinfection, rates of exposure, and age were examined. Although only 13 individuals showed positive rates of reinfection, there were statistically significant and independent effects of both exposure and age on reinfection rate. Quantitative estimates of reinfection rates suggested that individuals aged 12 years or less acquired substantially more infection (measured as egg output) than individuals more than 12 years old.
Proteinases inTrichomonas vaginalisandTritrichomonas mobilensisare not exclusively of cysteine type
Authors: Bózner P. , Demeš P. 
Published: June 2009

SUMMARYHigh molecular weight proteinases ofTrichomonas vaginalis(with apparentMrvalues 142 and > 220 kDa) andTritrichomonas mobilensis(Mr67, 86, 104 and 120 kDa), optimally active at pH 8, were analysed in gelatin-containing polyacrylamide gels. All of these proteinases were resistant to serine-, aspartic- as well as cysteine proteinase inhibitors. Both proteolytic bands inT. vaginalisand two proteinases inT. mobilensis(67 and 104 kDa) were inhibited by EDTA and EGTA suggesting that they belong to the metallo-proteinase class. The 67 kDa proteinase ofT. mobilensiswas inhibited also byo-phenanthroline. The other two bands ofT. mobilensis(86, 120 kDa) were not classified to any proteinase group since they appeared to be resistant to the chelating agents tested in this study.
Distinct, developmental stage-specific activation mechanisms of trypanosome VSG genes
Authors: Graham S. V. , Matthews K. R. , Shiels P. G. , Barry J. D. 
Published: June 2009

SUMMARYThe metacyclic form of African trypanosomes is the first to express genes for the Variant Surface Glycoprotein (VSG) and it uses an unusually predictable subset of the VSG gene repertoire. We have developed a model system for the analysis of metacyclic VSG (M-VSG) gene expression and have used this to demonstrate that, for two M-VSG genes, different modes of expression operate in the insect and mammalian phases of the life-cycle. In metacyclic-derived clones, these genes are expressedin situ, whereas they are routinely activated by duplication in bloodstream trypanosomes. The expression loci for both M-VSG genes studied are structurally simple and we present a model, based on this, for the maintenance of a separate M-VSG repertoire and expression system.
An investigation of fructose utilization in Acanthocheilonema viteae
Authors: Hayes D. J. , Carter N. S. 
Published: June 2009

SUMMARYThe capacity of Acanthocheilonema viteae to metabolize fructose was investigated in vitro. In common with other filarial species A. viteae oxidized fructose to lactate but its rate of consumption was only 40% of the glucose-containing control value. Fructose was not incorporated into glycogen. Release of 14CO2 from [U-14C]fructose was not detected in the presence of glucose and was about 40% of the glucose-containing value under conditions where fructose was the sole hexose substrate. Fructose consumption and lactate excretion increased in proportion to the external concentration of fructose. However, worm viability was not maintained in fructose over a 120 h in vitro incubation. In the presence of fructose, protein synthesis (measured incorporation of [35S]methionine into acid-insoluble material) was reduced compared to the glucose-containing control group; but was significantly greater than the value obtained under glucose-free conditions.
Antigen shedding from the surface of the infective stage larvae ofDirofilaria immitis
Authors: Ibrahim M. S. , Tamashiro W. K. , Moraga D. A. , Scott A. L. 
Published: June 2009

SUMMARYA qualitative and quantitative analysis was made of the release of surface-associated molecules from developingDirofilaria immitisinfective-stage larvae (L3).D. immitisL3s were labelled with125I using an Iodogen catalysed reaction and either maintained in culture or placed in chambers that were implanted into Lewis rats. The larvae released 10–20% of the labelled material each day during the first 4 days ofin vitroandin vivodevelopment. The loss of surface-labelled peptides from developing larvae corresponded with an increase in the amount of trichloroacetic acid-precipitable radioactivity found in the culture medium. SDS—PAGE analysis of the labelled material showed that the same 35 and 6 kDa components found in larval extracts were shed into culture medium by the developing parasites. Metabolic labelling studies and experiments in which larvae were labelled after different times in culture indicated that, once released, the surfaceassociated molecules were not replaced, and that this net loss of surface peptides resulted in a reduction in the antigenic potential of the cuticular surface. Antibodies from both immunized rabbits and naturally infected dogs immunoprecipitated the 35 kDa component. In contrast, the 6 kDa molecule was not recognized by the antibodies in any of the sera tested. Shedding of surface peptides and reducing surface antigenicity may represent mechanisms by whichD. immitisinfective-stage larvae evade immune attack.
Neurosecretory-like material in 3rd- and 4th-stageDirofilaria immitislarvae (Nematoda: Filarioidea)
Authors: Delves C. J. , Webb R. , Howells R. E. 
Published: June 2009

SUMMARYPhase-interference microscopic examination of the infective, post-infective 3rd-stage and 4th-stage larvae ofDirofilaria immitishas identified a single cell body in each of the paired lateral amphidial nerves which undergoes characteristic morphological change during the development from 3rd- to 4th-stage larvae. Acetaldehyde—fuchsin staining of worm sections revealed fuchsinophilic material in the precise location of the amphidial nerve-cell bodies observed by phaseinterference microscopy. This material was found in 70% of infective larvae recovered from mosquitoes and in 100% of larvae recovered from micropore chambers 24 h after implantation into BALB/C mice. In pre-moult larvae recovered at 42 h (Experiment 1) and at 48 h (Experiment 2) fuchsinophilic material was demonstrable, but no staining was observed in those larvae in which separation of the 3rd- and 4th-stage cuticles had occurred. No such material was observed in 4thstage larvae recovered from chambers after 74 h, and in these larvae the amphidial nerve-cell bodies were not discernible. These cytological observations are consistent with a cycle of elaboration and release of neurosecretion associated with moulting inD. immitis.
Adaptation of field strains ofRhipicephalus appendiculatusNeumann (Acarina: Ixodidae) to host resistance
Authors: Chiera J. W. , Newson R. M. , Karuhize G. R. 
Published: June 2009

SUMMARYA comparison of feeding and breeding performance was made between a laboratory strain (LS) and two freshly collected field strains (FS1, FS2) ofRhipicephalus appendiculatus. The LS had been cultured for over 30 years on tick-susceptible rabbits. When fed on susceptible rabbits LS produced smaller eggs and unfed larvae, nymphs and adults than those of FS. Eggs and larvae from females engorged on cattle were larger than those from females engorged on rabbits. LS and FS females engorged on susceptible hosts were of similar weight, but the FS females were twice as heavy as LS females when tick-resistant hosts were used. A higher proportion of LS ticks than of FS ticks engorged on susceptible hosts, but a lower proportion on resistant hosts. Thus on susceptible hosts LS showed a higher reproduction efficiency than FS, but a lower one than FS on resistant hosts. The proportional reductions of engorged weights and numbers feeding successfully on resistant hosts were significantly lower for LS than FS ticks. Cross-resistance was low between LS and FS. Although all strains were affected by host resistance, it was concluded that the field strains were better adapted to withstand resistance than the laboratory strain.
Identification of a trypanocidal factor againstTrypanosoma equiperdumin normal human serum
Authors: Verducci G. , Perito S. , Rossi R. , Mannarino E. , Bistoni F. , Marconi P. 
Published: June 2009

SUMMARYNormal human serum (HS) contains trypanolytic activity and agglutinins toTrypanosoma equiperdum, while such activities are not found in sera from a range of animals susceptible to infection. HS given toT. equiperdum-infected mice caused a rapid decrease in the number of circulating trypanosomes and protection from lethal infection. Trypanolytic activity of human serum was found to be associated, after DEAE chromatography and Sephadex G-200 gel filtration, with the fraction containing 19S antibodies. Immunofluorescence assays confirmed a binding of human IgM and C1qcomplement component onto the surface ofT. equiperdum. Anti-T. equiperdumactivity of HS was specifically directed toT. equiperdumsurface components and not to some mouse serum components adsorbed on parasites during the growth in the host, because HS adsorbedin vivoin CD-1 mice retained full protective and agglutinating properties. Trypanocidal activity appears in human serum about the 7th month after birth and persists until late in life. On the contrary, human purified high-density lipoprotein had no significantin vitroorin vivotrypanocidal activity. In conclusion, strong natural anti-T. equiperdumactivity in human serum was mainly mediated by natural antibodies of the IgM class. The presence of natural IgM active againstT. equiperdumin HS could represent one of the natural mechanisms of resistance of refractory hosts against trypanosome infections. This phenomenon provides further evidence that host specificity of trypanosomes may be partly conditioned by the presence of natural antibodies.
Aerobic to anaerobic transition in the carbohydrate metabolism of Schistosoma mansoni cercariae during transformation in vitro
Authors: Van Oordt B. E. P. , Tielens A. G. M. , Van Den Bergh S. G. 
Published: June 2009

SUMMARYSchistosoma mansoni cercariae in water were shown to possess a largely aerobic energy metabolism, the Krebs cycle being the main terminal of carbohydrate breakdown. A metabolic transition towards a more anaerobic breakdown of carbo-hydrate could be achieved by incubation conditions which also stimulated biological transformation. Incubation of cercariae in a simple salt medium containing 5 mM glucose induced such a metabolic transition: beside carbon dioxide large amounts of lactate and pyruvate were excreted. The results indicate that the production of pyruvate was coupled to electron transfer in the respiratory chain. Some aspects of this unusual pyruvate production are discussed. The observed change in the end-product pattern of carbohydrate breakdown is very rapid: most of the switch occurred within 2 h. Our results show that the metabolic transition was triggered by the biological transformation itself, or by the same event that induces the biological transformation. The metabolic and the biological changes proceeded synchronously.