bluuebunny/crossref_metadata_2025 huggingface dataset:
Structure and development of the spermatozoon of the parasitic nematode, Nematospiroides dubius
Authors: Wright E. J. , Sommerville R. I.
Published: June 2009

Spermatogenesis and sperm maturation in Nematospiroides dubius were studied using electron microscopy. The testis is telegonic and germ cells in the zones of mitosis, growth and meiosis are connected by a central anucleate mass of cytoplasm, the rachis. The early part of spermatogenesis is dominated by the synthesis and growth of membrane-bound vesicles called membranous organelles, which originate from RER-associated Golgi bodies. Following meiosis the spermatids separate from the rachis and their chroinatin, which is no longer bounded by a nuclear envelope, condenses into an arrow-head shape and is extruded to form a tail-like structure. After insemination spermatozoa undergo a profound change called activation. The cytoplasmic region which was previously long and cylindrical becomes spherical and the membranous organelles which lined its perimeter fuse with the plasma membrane and become confined to the posterior hemisphere of the sperm, close to the nuclear tail. The anterior half of the sperm is devoid of organelles but contains many filaments organized into clumps and chains; this region being responsible for amoeboid locomotion of the sperm.
Host life-history variation in response to parasitism
Authors: Minchella D. J.
Published: June 2009

Over half of all living species of plants and animals are parasitic, which by definition involves intimate association with and unfavourable impact on hosts (Price, 1980). This paper will only consider parasites whose ‘unfavourable impact’ adversely affects the birth and/or mortality rates of their hosts (Anderson, 1978). Most organisms are potential hosts and must deal with the problem of parasitism. The probability of parasitic infection of a host is influenced by both environmental and genetic factors. Traditionally it was assumed that a host was either resistant or susceptible to a particular parasite and therefore the interaction between a parasite and potential host had only two possible outcomes: either the resistant host rebuffed the parasitic attack and remained uninfected or the parasite successfully invaded and significantly reduced the reproductive success of the susceptible host. This approach, however, ignored the intraspecific genetic variation present within both host and parasite populations (Wakelin, 1978). Since the outcome is determined by the interaction of a finite set of host genes and parasite genes, genetic variation in host susceptibility and parasite infectivity (Richards, 1976; Wakelin, 1978) suggests that more than two outcomes are possible. Variation in host and parasite genomes does not begin and end at the susceptibility/infectivity loci. Other genes may also influence the outcome of host–parasite interactions by altering the life-history patterns of hosts and parasites, and lead to a variety of outcomes.
Factors affecting the acquisition of resistance againstSchistosoma mansoniin the mouse. IV. The inability of T-cell-deprived mice to resist re-infection, and otherin vivostudies on the mechanisms of resistance
Authors: Doenhoff M. , Long E.
Published: June 2009

CBA mice deprived of their T-cells by means of thymectomy and administration of rabbit anti-mouse thymocyte serum before a primary infection ofSchistosoma mansoni, failed to resist re-infection to the same extent as immunologically intact controls. However, little difference was made to the degree of resistance to re-infection acquired by thymectomizedS. mansoni-infected mice when the anti-thymocyte serum was administered after the primary infection and just before the challenge. Hydrocortisone acetate, when administered to primarily infected mice just before reinfection appeared to reduce the degree of acquired resistance, but the drug also had a schistosomicidal effect on the challenge-derived organisms. An attempt to specifically suppress the acquisition of resistance againstS. mansoniby administering serum from homologously infected, resistant donors before and during the course of a primary infection failed, and partial depletion of complement activity with cobra venom factor that was administered just before challenge also failed to affect resistance. Serum obtained from mice with chronicS. mansoniinfections and injected intradermally at the site of subsequent administration of a homologous percutaneous challenge infection failed to markedly inhibit maturation of the challenge in the recipient. Recipients of 3 ml of serum from heavily infected donors were also not significantly more resistant to challenge than untreated controls. However, isolated skin from heavily infected mice allowed fewer cercariae to penetrate and emerge transformed as schistosomula than did isolated skin from uninfected controls.
Schistosoma mansoni: evidence for a role of serum factors in protecting artificially transformed schistosomula against antibody-mediated killing in vitro
Authors: Tavares C. A. P. , Soares Rita C. , Coelho P. M. Z. , Gazzinelli G.
Published: June 2009

Artificially transformed schistosomula of Schistosoma mansoni develop a consistent but small protection against the lethal effects of antibody plus complement when cultured for 24 h in a chemically defined medium. In contrast, they become rapidly resistant to antibody plus complement, when cultured in the presence of a complex medium consisting of equal parts of heat-inactivated rabbit serum and Earle's/lactalbumin or in defined medium supplemented with small amounts of heat-inactivated rabbit serum. Sephadex G-200 gel filtration revealed that the protective factor in rabbit serum is a macromolecule with a molecular weight between 7 and 19S. Parasites cultured at 10 °C or in the presence of 200 μg of puromycin show less serum-induced protection against the lethal effects of antibody plus complement than do controls.
Infections with blood parasites in the small British rodentsApodemus sylvaticus,Clethrionomys glareolusandMicrotus agrestis
Authors: Healing T. D.
Published: June 2009

Three populations of small wild British rodents were studied by capture–recapture methods over a period of 3 years, a fourth group was studied for 1 year and a fifth was sampled annually for 4 years. Blood smears were taken from 3 species of rodents: the woodmouseA podemus sylvaticus, the bank voleClethrionomys glareolus(and an island sub-speciesC.g. skomerensis) and the short-tailed voleMicrotus agrestis. The smears were examined microscopically. Four genera of haemoparasitesBabesia, Hepatozoon, TrypanosomaandGrahamellawere detected.Babesiawas absent fromC.g. skomerensis, Hepatozoonwas rarely found inA. sylvaticusandM. agrestisandTrypanosomawas rare inA. sylvaticus. More males were infected than females but the difference was only statistically significant for the infection withHepatozoonin adultC.g. skomerensis. Infections withBabesiaandHepatozoonwere more prevalent in adult animals and infections withTrypanosomawere more prevalent in younger individuals. Only inC.g. skomerensiswas there a significant difference between age classes in the prevalence of infection withGrahamella– there being more adults infected. Concurrent infections were detected,Hepatozoonbeing the parasite most commonly involved. The prevalence of infections was found to be approximately proportional to the number of animals known to be alive, regardless of the season.
Ultrastructural evidence for complement and antibody-dependent damage to schistosomula of Schistosoma mansoni by rat eosinophils in vitro
Authors: McLaren Diane J. , Ramalho-Pinto F. J. , Smithers S. R.
Published: June 2009

Rat peritoneal eosinophils adhere to live Schistosoma mansoni schistosomula in vitro in the presence of fresh normal rat serum, or in heat-inactivated serum from rats immune to the parasite. When the eosinophils are present in sufficient numbers the worms show ultrastructural evidence of surface damage and are ultimately killed. It is believed that the appearance of focal lesions in the tegument of the schistosomulum follows the secretion of enzymes by the eosinophils onto the parasite surface. The cells have been observed within these lesions and later between the basal plasma membrane of the tegument and the underlying interstitial material. It is suggested that the cells are responsible for prising the tegument away from the body of the worm. The detached tegument shows evidence of further degradation. Adherent eosinophils which have released their secretions appear to degenerate and are eventually replaced by macrophages. Remnants of both the expended eosinophils and the disrupted tegument have been identified within the macrophages. Adherence of eosinophils through C3–C3 receptor interaction results in earlier and more severe damage to the schistosomula than when adherence occurs through Fe receptors. Rat eosinophils also adhere to C3-coated, glutaraldehyde-flxed schistosomula and C3-coated Sepharose beads. However, evidence of enzyme secretion is only obtained when the target is a schistosomulum.
Laboratory comparison of the relative success of Biomphalaria glabrata stocks which are susceptible and insusceptible to infection with Schistosoma mansoni
Authors: Minchella D. J. , Loverde P. T.
Published: June 2009

A method of interrupting the life-cycle of the human blood fluke Schistosoma by increasing the proportion of genetically insusceptible intermediate host snails in natural populations was first proposed nearly 25 years ago. The method assumes that insusceptible snails will be at a selective advantage over susceptible snails when the schistosome parasite is present, and therefore natural selection will act to increase the proportion of alleles for insusceptibility. A major objection to the proposed technique is ‘If insusceptible snails are at a selective advantage, then why are they not predominant in natural populations that transmit disease?’ One explanation of this paradox is that insusceptibility may be associated with a disadvantageous character or a physiological defect. This study tests this hypothesis by measuring the relative reproductive success of susceptible and insusceptible snails under controlled conditions. Results indicate that insusceptible (unsuitable) snails are negatively affected in the presence of either susceptible snails or schistosome parasites. Furthermore, in the presence of both susceptible snails and schistosome parasites, insusceptible snails are selectively disadvantaged compared to susceptible snails. These results obtained under laboratory-controlled conditions suggest a plausible answer as to why insusceptible snails are not predominant in natural populations that transmit disease.
Retarded development of Schistosoma mansoni in immunosuppressed mice
Authors: Harrison R. A. , Doenhoff M. J.
Published: June 2009

Previous observations, which showed that treatment of mice with hydrocortisone acetate around the time of their infection with Schistosoma mansoni reduced the mature worm burden, have been confirmed. The number of eggs produced by the surviving worms during early patency was also significantly reduced. Cyclophosphamide and another steroid immunosuppressant, betamethasone, also caused a reduction in fecundity of S. mansoni when given at the time of infection, as did T-cell deprivation of the mice by adult thymectomy and injection of anti-thymocyte serum 1 month before infection. There was no effect of these three treatments on worm numbers. In contrast, injection of mice with anti-thymocyte serum at the time of infection marginally increased the size of the mature worm burden. The deleterious effects of hydrocortisone acetate on S. mansoni worm numbers and fecundity were only apparent if the steroid was given within 1 week of infection. Indomethacin, a compound which inhibits tissue inflammatory reactions by inhibiting prostaglandin synthesis, and which therefore mimics one of the actions of corticosteroids, had no effect on S. mansoni worm maturation and fecundity.
Nippostrongylus (Nematoda) in protein-malnourished rats: host mortality, morbidity and rehabilitation
Authors: Keymer Anne , Crompton D. W. T. , Walters D. E.
Published: June 2009

The synergistic relationship between host nutrition and the effects of Nippostrongylus was investigated experimentally in rats fed a diet containing 1% (w/w) protein. Rats were infected with 10 doses of N. brasiliensis varying from 0.35 to 99 larvae/g and their daily food intake and weekly body mass were compared with those of uninfected rats fed the same diet for a period of 9 weeks. The deterioration of the uninfected rats observed as a result of protein-energy malnutrition was found to be accelerated in a dose-dependent manner in the rats infected with N. brasiliensis. Analysis of food intake and body mass measurements demonstrated that this acceleration was related to a decrease in food intake and indicated a likely alteration in nutrient utilization, both of which were established by the end of the first week of the infection. Remission from the combined effects of malnutrition and infection was achieved by offering the rats a high-protein diet (20% w/w), whereupon rehabilitation was found to be complete within a period of 9 days. The implications of the results and the possible mechanisms involved in their generation are discussed in relation to the frequent coexistence of helminthiasis and malnutrition.
Ovoviviparity in platyhelminth life-cycles
Authors: Tinsley R. C.
Published: June 2009

The encapsulated embryos of platyhelminths may be retained and complete their developmentin uteroin a range of circumstances. However, hatching within the parent (the criterion of ovoviviparity) is relatively rare and larvae generally emerge only after deposition. Viviparity is characterized by the nutritional dependency of the unencapsulated larva upon the parent, but in several cases larvae retained within a shell also receive parental nutrients during intra-uterine development. Uptake of exogenous nutrients via shell pores occurs inSchistosoma mansonibut the eggs, which gain all the advantages of intra-uterine retention, are supported by host nutrients.

Intra-uterine larval development avoids the hazards of development in the external environment and eliminates the time delay between oviposition and infection. Deposition of immediately infective offspring may be concentrated in time and space to exploit periods of host vulnerability. The control and precision of transmission is illustrated by examples in which the opportunity for invasion is restricted because of either host behaviour or environmental instability. This strategy has been an important factor in the evolution of polystomatid monogeneans, and its effectiveness is demonstrated by comparison of the life-cycles ofPolystoma integerrimumandPseudodiplorchis americanus. Ovoviviparity also increases reproductive potential in some polystomatids by extending the period of multiplication and by increasing established populations through internal re-infection. InEupolystoma alluaudi, the capacity for ovoviviparity is programmed into larval development and this regulates population growth within individual hosts.
Interactions betweenTrypanosoma bruceiandBabesiaspp. andPlasmodiumspp. in mice
Authors: Millott Stephanie M. , Cox F. E. G.
Published: June 2009

Swiss mice with chronicTrypanosoma bruceiinfections become refractory to subsequent infection withBabesia microtiandB. rodhaini. Infection withB. microti7 days afterT. bruceiresulted in an obvious inhibition of the babesia parasitaemias and this inhibition became more profound as the time interval between the infections increased, until at 17–20 days the parasitaemias were totally abolished. Even after intravenous injection of large numbers of parasites parasitaemias were inhibited. Similar inhibition was obtained in BALB/c mice but not in C57BL/6 mice. Mice with establishedT. bruceiinfections also showed reduced susceptibility toB. rodhaini. In mice similarly infected withT. bruceiand the malaria parasitesPlasmodium chabaudi chabaudiandP. c. adamithe pre-patent periods were noticeably prolonged but the subsequent parasitaemias were unaffected. Infections withP. yoeliiwere unaffected.Trypanosoma bruceiinfections were not affected by the intracellular parasites. Among the mechanisms investigated to explain these findings were changes in red blood cell populations, cross-reacting antigens, the release of toxic factors and the generation of activated oxygen species. None of these could account for the inhibition observed.
The influence of environmental temperature upon transmission of the cercariae of Echinostoma liei (Digenea: Echinostomatidae)
Authors: Evans N. A.
Published: June 2009

The survival and infectivity characteristics of the cercariae of Echinostoma liei are described for 6 different water temperatures in the range 12–40 °C. Cercarial survival steadily decreased with increasing temperature, the maximum survival time falling from 75 h at 12 °C to approximately 8 h at 40 °C. Changes in environmental temperature affected the infectivity even of freshly emitted cercariae but their most noticeable effect was upon the rate at which infectivity diminished with increasing cercarial age. Infectivity rose from zero at 12 °C to a maximum at 30 °C before declining to a low level at 40 °C. The transmission efficiency of the cercariae at each temperature was calculated as the ratio of the instantaneous per capita rates of mortality and infection respectively. The efficiency of transmission was high between 19 and 30 °C, suggesting that cercariae are well adapted for transmission at water temperatures likely to be encountered in natural habitats.
Changes in the surface ofDipetalonema viteae(Filarioidea) during its development as shown by comparative peptide mapping
Authors: Baschong Werner
Published: June 2009

The cuticle of parasitic nematodes, the main contact site with the host, plays an important role in host-parasite interaction and thus also in immunological control. We compared different surface-iodinated life-stages of the filarial wormDipetalonema viteae(microfilariae, infective 3rd-stage larvae (L3), adult males and females) with respect to changes in their surface composition. Autoradiographs of peptide maps show that all stages present an identical set of peptide spots reflecting common surface protein(s). Spots specific for larvae L3show that the composition of the iodinated surface differs in microfilariae and adults i.e. it changes during development. Adults show a spot typical for males or females. Identical spots are found in L3. This suggests that a surface component is also sex specific.
The isolation and characterization of a Babesia from red deer (Cervus elaphus)
Authors: Adam Katherine M. G. , Blewett D. A. , Brocklesby D. W. , Sharman G. A. M.
Published: June 2009

On three occasions, antibody positive blood from wild red deer produced overt infections with Babesia when inoculated into splenecto-mized red deer. One of the deer also became infected with Eperythrozoon sp. Babesia divergens, B. capreoli and the Babesia of red deer are morphologically similar and the marginal position of the parasites in the host cell is characteristic. Babesia were not seen and no antibody was formed in five out of six splenectomized bovine calves which were injected with parasitaemic red deer blood. Two of these calves when challenged with B. divergens were fully susceptible. A transient infection with the deer Babesia may have occurred in the sixth calf since antibody was detected and the animal resisted challenge with B. divergens.In indirect fluorescent antibody tests there was little or no difference in the titre of sera from naturally or experimentally infected cattle and deer when reacted with B. divergens or the red deer Babesia antigens. Despite their similarities, specific status for B. divergens and the red deer Babesia is probably justified; at present there is insufficient evidence to justify separation of the red deer Babesia from B. capreoli.
Linked metabolism of L-serine and L-alanine by Moniliformis moniliformis (Acanthocephala) in vitro
Authors: Ward P. F. V. , Crompton D. W. T.
Published: June 2009

Experiments to investigate the linked metabolism of L-serine and L-alanine by Moniliformis moniliformis in vitro were carried out by incubating adult worms aerobically for 3 h at 37 °C in Tyrode’s solution containing L-[U-14C]alanine and other amino acids. When present in the medium alone, alanine was totally removed by the worms and metabolized almost entirely to ethanol and a compound identified as carbon dioxide. When present in the medium with serine and no other amino acids, alanine was largely metabolized as before but additional alanine, believed to originate from serine, was excreted. The same results were obtained with serine and 16 other amino acids in the incubation medium.
Echinococcus granulosus: in vitroeffect of monensin on the tegument of the protoscolex
Authors: Rogan M. T. , Richards K. Sylvia
Published: June 2009

Protoscoleces ofEchinococcus granulosuswere incubated in a 10 μm solution of monensin and their viability and the ultrastructure of their tegument were monitored over a 36 h period. The earliest effects of the lonophore, apparent within 15 min, involved a degree of cisternal swelling of the tegumentary Golgi complexes. Swelling became more pronounced with time and cytons eventually contained numerous large electron-lucent vesicles. Residual bodies indicative of autophagy were observed in the cytons and distal cytoplasm from 1 h onwards. All movement of protoscoleces ceased after 1 h and the surface of the soma subsequently became folded, possibly suggesting spastic paralysis. Later, vacuoles and large cytoplasmic blebs were observed in the distal cytoplasm and viability dropped rapidly after 12 h. All protoscoleces were dead at 36 h. The potential of monensin as anin vivoprotoscolicidal agent is discussed.
Studies on two new species of Microsporida hyperparasitic in adultAllocreadium fasciatusi(Trematoda, Allocreadiidae)
Authors: Canning Elizabeth U. , Madhavi R.
Published: June 2009

The vegetative and sporogonic stages ofUnikaryon allocreadiisp. nov. andNosema giganticasp. nov., from the parenchyma of adult flukes,Allocreadium fasciatusiin the gut of the freshwater fishAplocheilus melastigmafrom India, are described and figured.U. allocreadii, which is uninucleate throughout development and is disporoblastic, differs fromU. legeriin that it occurs in adult flukes from a freshwater host.N. giganticahas diplokaryon nuclei, at least in the sporogonic stages, and is much larger than all other microsporidia in platyhelminths.

Hatching of the spores and patholgenicity are described and the mode of transmission to the flukes is discussed. Infected flukes, which are sluggish and opaque, are often displaced from the normal site of infection.
Experimental parasitization of larvae of the gypsy moth, Porthetria dispar (L.), with the entomogenous fungus, Beauveria bassiana (Balsamo) Vuill
Authors: Wasti S. S. , Hartmann G. C.
Published: June 2009

Second-instar larvae of the gypsy moth, Porthetria dispar (L.) were infected with Beauveria bassiana (Balsamo) Vuill. by allowing larvae to crawl over sporulating cultures of the fungus. Virulence of the pathogen was increased by inoculating larvae of the wax moth, Galleria melonella (L.), twice in serial succession. Observations were made on the infectivity and histopathology of the parasite in the host. Penetration of the cuticle occurred 24 h after inoculation and at 64 h post-inoculation the interior was completely filled with hyphae. Penetration of the gut wall was also observed.
Passive transfer of acquired resistance to Schistosoma mansoni in laboratory mice
Authors: Sher A. , Smithers S. R. , Mackenzie Pamela
Published: June 2009

Serum taken from mice 12–15 weeks after a primary infection of Sehistosoma mansoni transfers to normal recipients a partial resistance to subsequent schistosome challenge. The transfer of immunity is evident not oniy in the reduced recovery of mature parasites from the liver, but also in the diminished numbers of invading schistosomula recovered from the lungs. Since the recipients of immune serum exhibit a level of resistance equivalent on average to 47 % of that found in actively immunized animals, the results suggest that humoral factors play a major role in the effector mechanism of schistosome immunity.
Studies to determine the taxonomic status of Eimeria mitis, Tyzzer 1929 and E. mivati, Edgar and Seibold 1964
Authors: Shirley M. W. , Jeffers T. K. , Long P. L.
Published: June 2009

We have examined several taxonomic features of a number of strains of Eimeria from many sources world wide. The strains were isolated on the basis of their small spherical (or sub-spherical) oocysts. From a study of mean oocyst dimensions, electrophoretic variation of enzymes, ability to develop in embryonated eggs, absence of gross lesions in heavily infected chickens, and cross-immunity, all the strains were found to belong to one species. For convenience, the parasites when isolated, were referred to as strains of E. mitis/mivati-type, but after characterization they were clearly found to be E. mitis. In contrast, a laboratory strain of E. mivati supplied to one of us (M.W.S.) was found to be a mixture of E. acervulina and E. mitis. Evidence from these and other studies supports the notion that E. mivati is a nomina dubia.
Host cell invasion by Apicomplexa: an expression of the parasite's contractile system?
Authors: Russell D. G.
Published: June 2009

Recent studies on the motility of coccidian sporozoites have demonstrated a membrane-associated contractile system capable of moving certain intramembraneous components down the parasite surface propelling it forwards. The properties of this system resemble recorded observations on host cell invasion. In this study the invasive behaviour ofEimeria tenellaandE. acervulinahas been examined, with reference to the above findings, by light microscope and scanning and transmission electron microscopes. Known inhibitors of motility prevent invasion, though attachment appears unaffected. Invasion itself consists of 3 phases; attachment and orientation, induction of a parasitophorous vacuole and translocation of the parasite into the vacuole. Ultrastructural examination reveals a close membrane/membrane association maintained throughout invasion. From these results it is suggested that the parasite enters the parasitophorous vacuole by ‘capping’ the host/parasite junction down its body, so locomoting into the host cell. Such a model has two main advantages; it requires no additional modifications to either cell, and the specificity of membrane receptors would enable the one membrane-associated contractile system to be responsible for locomotion, antibody capping and host cell invasion.
The structure of the mature oocyte and zygote of Corynosoma semerme (Acanthocephala)
Authors: Peura Raija , Valtonen E. Tellervo , Crompton D. W. T.
Published: June 2009

Observations made with the transmission electron microscope are described from the free ovaries of sexually mature female Corynosoma semerme (Palaeacanthocephala) from the ringed seal (Pusa hispida). The structure of the mature ovaries consists of a supporting syncytium, oogonial cells and tissue and appears to be basically similar to that already described for 4 other species of Acanthocephala representing the 3 orders of the phylum. A comparison has been made between the organization of the cytoplasm of the mature oocyte and the zygote with reference to the consequences of fertilization. A detailed description is presented of the heterogeneous inclusions that are observed in the cytoplasm of the mature oocyte but not in the zygote. The fate and possible function of the components of these inclusions is discussed.
Immunization of mice with gamma-irradiated intramuscularly injected schistosomula of Schistosoma mansoni
Authors: Bickle Q. D. , Taylor M. G. , Doenhoff M. J. , Nelson G. S.
Published: June 2009

The parameters involved in the induction of resistance against Schistosoma mansoni by injection of irradiated, artificially transformed schistosomula were studied in mice. Single intramuscular injections of 500 schistosomula exposed to radiation doses in the range 2·3 to 160 krad. resulted in significant protection (in the range 20 to 50% as assessed by reduced worm burdens) against a challenge infection administered at intervals from 3 to 24 weeks post-vaccination. However, schistosomula irradiated with 20 krad. consistently resulted in better protection than those exposed to either higher or lower radiation doses despite the persistence of stunted adults from the infections irradiated with 2·3 krad. Vaccination with 40 krad. schistosomula resulted in significant protection in terms of reduced worm and tissue egg burdens and increased survival following lethal challenge. Varying the number of irradiated schistosomula, the frequency and route of their administration, the site of challenge and the strain of host all failed to enhance the level of resistance. However, percutaneously applied, irradiated cercariae were found to be more effective in stimulating resistance (60%) than intramuscularly injected, irradiated schistosomula (40%).
Gametocytogenesis of Plasmodium falciparum in vitro: the cell-cycle
Authors: Sinden R. E. , Smalley M. E.
Published: June 2009

Reproducible growth of gametocytes of Plasmodium falciparum in vitro was obtained from ring-stages taken directly from naturally infected patients and from the same material following storage in liquid nitrogen. Progressive sexual differentiation in vitro was examined for a finite period of 9 days in microcultures and was, for convenience, divided into 5 stages using established morphological criteria (Hawking, Wilson & Gammage, 1971). This microculture system was adapted as a bioassay for various anti-metabolites. Drug activity was measured by observing the inhibition of the established pattern of sequential development in experimental as compared to control cultures. Inhibitors used were directed against DNA, RNA and protein metabolism and microtubule assembly. As a result of these studies it is proposed that the sexual cell-cycle of P. falciparum is characterized by 4 phases. (1) A G1 period which lasts only a few hours. (2) The S phase, where DNA synthesis occurs, occupies the remainder of the first 2 days of development – both G1 and S are confined to stage I and II gametocytes. (3) G2, which is subdivided into 2 sections: G2A, characterized by stage II and III gametocytes, in which significant RNA and protein synthesis continue to occur; and G2B, where there is a progressive increase in transcription control resulting in the depression of both RNA and protein synthesis. Nonetheless, continued morphological differentiation occurs in the latter section transforming the parasites to stage IV and the morphologically and functionally mature stage V. The final M phase is marked by the brief and explosive events of gametogenesis, during which further protein synthesis occurs de novo. The proposed cell-cycle is examined as a model for studies on the activity of gametocytocidal compounds.
Immunological aspects ofGiardia murisandSpironucleus murisinfections in inbred and outbred strains of laboratory mice: a comparative study
Authors: Brett Sara J. , Cox F. E. G.
Published: June 2009

The intestinal flagellates,Giardia murisandSpironucleus muris, cause similar infections in CBA mice as determined by trophozoite and cyst counts. Both parasites occur all along the small intestine withG. muris, being mainly present in the anterior part andS. muristowards the posterior. The early stages of infection are similar in all strains of mice examined and peak levels of both trophozoites and cysts occur 1–2 weeks after infection. All strains of mice overcome the infection but the rate of recovery varies considerably between strains, being most rapid in BALB/c and slowest in A and C57BL.B10. Outbred mice are more variable in their recovery than inbred mice. After recovery, mice are partially resistant to reinfection with the homologous but not the heterologous parasite. Resistance to reinfection withS. murisis greatest in those strains that eliminate the primary infection most rapidly.Giardia murisandS. muriscause similar changes in the mucosa of the small intestine of BALB/c mice with increased intra-epithelial lymphocyte counts from 3 weeks onwards corresponding with the start of the elimination of the parasites from the gut. A reduction in villus height and increase in crypt depth is also characteristic of these infections.
Ethidium bromide: pharmacokinetics and efficacy against trypanosme infections in rabbits and calves
Authors: Gilbert R. J. , Newton B. A.
Published: June 2009

[14C[ethidium bromide has been used to determine drug levels in tissues and body fluids of rabbits and calves following intramuscular injection. Uninfected andTrypanosoma brucei- orTrypanosoma congolense-infected animals were studied. Blood and tissue fluid levels reached a maximum within 1 h and then fell rapidly; after 96 h 80–90% of the radioactivity injected had been excreted, approximately one third in urine and two thirds in faeces. By 1 h after injection of 1 mg [14C]ethidium/kg into aT. congolense-infected calf, 70–80% of the radioactivity in blood was found to be bound to trypanosomes. Doses of 1 or 10 mg/kg were found not to be curative forT. congolenseorT. bruceiinfections in rabbits; drug treatment resulted in a period of sub-patent parasitaemia which was always followed by a relapse. Examination of the prophylactic action of ethidium in rabbits showed that the drug extended the pre-patent period following trypanosome inoculation but provided no absolute protection. A period of ‘apparent’ prophylaxis observed after drug treatment of infected rabbits has been correlated with the presence of anti-trypanosome IgG in the serum.
Occurrence of fibronectin antigenic determinants onSchistosoma mansonilung schistosomula and adult worms
Authors: Ouaissi M. A. , Cornette J. , Capron A.
Published: June 2009

Fibronectin determinants were revealed in a soluble extract ofSchistosoma mansoniadult worms by standard immunodiffusion and immunoelectrophoresis techniques. The same target molecules were demonstrated on the parasite's surface using a binding assay with [125I] anti-fibronectin. The use of fluorescein- and peroxidase-conjugated antibodies confirmed the above observations and provided a fairly precise means for locating the cross-reacting antigen on the worm surface. Anin vitrocytotoxic assay using inactivated (56°C, 2 h) anti-fibronectin rabbit immune serum and guinea-pig serum as a source of complement was developed. In these conditions, anti-fibronectin exerted cytotoxic activity against lung schistosomula and adult worms but not skin schistosomula. The ultrastructural damage induced by anti-fibronectin in the presence of complement was studied using transmission electron microscopy. The results suggest a close association between fibronectin determinants andS. mansonimembrane.
Fecundity-reducing pheromone in Argas (Persicargas) arboreus (Ixodoidea: Argasidae)
Authors: Khalil Galila M.
Published: June 2009

Fed adult Argas (Persicargas) arboreus produce a fecundity-reducing pheromone which affects all or most females in crowded conditions. Unfed adults and unfed and fed nymphs do not produce this pheromone. The effect of this pheromone is probably additive, increasing with additional crowding of adults. Mechanical disturbance is excluded as the cause of fecundity reduction. Fed females separated by a perforated barrier from crowded adults also exhibit very low fecundity. Adult excretory materials used 31 days post-feeding do not contain the fecundity-reducing pheromone. Preliminary experiments suggest that this pheromone is spatially limited in action, does not affect gonadotropic hormone synthesis and/or release, and does not induce oviposition deterrence behaviour. This may be considered to be a primer pheromone, causing alteration in normal vitellogenin synthesis and/or uptake and deposition in oocytes. The source and chemical nature of this pheromone should be investigated.
The open-field behaviour of mice infected with Trichinella pseudospiralis
Authors: Rau M. E.
Published: June 2009

The behaviour of mice exposed to graded doses of Trichinella pseudospiralis larvae was monitored in an open-field situation. Ambulatory activity declined briefly during the acute phase of the infection (day 11) but regained pre-infection levels 1 week later. Animals receiving heavy doses of T. pseudospiralis exhibited a mild increase in the level of ambulatory activity during the chronic phase of the infection. The infections did not affect the level of exploratory activity. The effects of the T. pseudospiralis infections on the behaviour of the mouse host were much less pronounced than those induced by T. spiralis. It is suggested that these differences may be associated with the small size of T. pseudospiralis and the lack of capsule formation.
Schistosoma mansoni: a comparative study of schistosomula transformed mechanically and by skin penetration. Electrophysiological responses to a wide range of substances
Authors: Thompson D. P. , Pax R. A. , Bennett J. L.
Published: June 2009

Volume conducted potentials were recorded from schistosomula ofSchistosoma mansonitransformed mechanically (MS) and by skin penetration (SS). The spontaneous electrical activity recorded consisted of bi and triphasic transients ranging from 20 to 200 μV in amplitude and 10 to 300 msec in duration. Low amplitude potentials occurred at a much greater frequency than large amplitude potentials, which appeared to correlate with peristaltic-like contractions of the schistosomulum's musculature. Electrical activity in the schistosomulum was highly sensitive to a number of agents believed to affect metabolic pathways, the neuromuscular system or the host/parasite interface of adult schistosomes. Among the most reactive substances were potassium antimony tartrate, eserine, poly-L-arginine and potassium cyanide. Over a wide range of experimental treatments, electrophysiological responses in schistosomula transformed from cercariae by mechanical decaudation and skin penetration were remarkably similar, supporting the notion that MS are suitable material forin vitroimmunochemical, biochemical and physiological study. Some treatments, however, were more or less effective in altering electrophysiological activity and motility in the schistosomulum than in adultS. mansoni. This suggests that significant physiological alterations may occur during development from skin stage to adult parasites concomitant with immunochemical and morphological changes already known to occur.
The structure of the intestine of Nematodirus battus and changes during the course of aninfection in lambs
Authors: Lee D. L. , Martin Jean
Published: June 2009

The structure of the intestine of adult Nematodirus battus is described. It is similar tothe intestine of some other trichostrongyles but with a few minor differences. Changes in the structure of the intestinal cells are described in N. battus taken from lambs during the later stages of an infection (days 20 to 32) with 60000 infected larvae. The mostnoticeable changes were a decrease in the amounts of glycogen and smooth endoplasmic reticulum, a reduction in the numbers of secretory-type granules and the appearance of vacuoles within the cells. Some of these vacuoles contained small crystals, and crystals, some of them large, were also found in the intestinal lumen. These changes, with the exception of the appearance of the crystals, are similar to changes described for Nippostrongylus brasiliensis affected by the immune response of the rat host, and it is concluded that the changes in N. battus could have been initiated by an immune response to this nematode in the lamb. Lambs given 2000 larvae of N. battus do not reject the nematodes in 32 days, and no changes were observed in the structure of these nematodes.
Formation of the cyst wall and related changes in the structure of the tegument ofBucephalus haimeanus(Lacaze-Duthiers, 1854) during its metamorphosis from the cercarial to the metacercarial stage
Authors: Higgins J. C.
Published: June 2009

The formation of the cyst wall surroundingBucephalus haimeanusand the related changes in the parasite tegument during its metamorphosis from the cercarial to the metacercarial stage have been investigated by means of experimental infections inGobiusculus flavescens. The initial fibrous cyst wall is formed from secretions produced by both the anterior gland cells and the tegument of the parasite. These secretions gradually become compacted against the surrounding hepatic cells until by the 20–30th day post-infection the 3-zoned inner layer, characteristic of the fully developed cyst wall, is formed. Hepatic cells immediately adjacent to this inner cyst wall layer are disrupted by the arrival of the metacercaria and form the middle vacuolated layer. As the metacercaria grows, the cyst increases in size causing still further hepatic cells to become flattened and incorporated into the cyst structure forming the outer nucleated layer. The structure of the cercarial tegument is described. Development of the metacercarial tegument is accomplished by the sequential movement of secretory vesicles from tegumental cell bodies into the outer cytoplasmic tegument. Vesicles of the types V. 1–5 are released from the outer cytoplasmic tegument, resulting in an almost complete breakdown of this layer prior to its replacement by the tegument of the fully developed metacercaria. The latter is characterized by the V. 6–9 type vesicles, dorso-ventrally flattened spines which terminate in 5–7 digits and by sensory cilia.
Light and gravity responses of the oncomiracidium ofEntobdella soleaeand their role in host location
Authors: Kearn G. C.
Published: June 2009

The behaviour of oncomiracidia of the monogenean skin parasiteEntobdella soleae, after hatching without chemical stimulation, has been studied in vertical, 4 cm high chambers illuminated from above. Most freshly hatched larvae are photo-positive and swim to the top of the vessel, where they remain actively swimming. Occasionally larvae become photo-negative and make a brief excursion to the bottom of the vessel. As the larvae grow older, these photo-negative excursions become more frequent and larvae spend progressively longer in the photo-negative phase of behaviour, but, even after many hours, photo-positive vertical excursions are still occurring. If this pattern of alternating photo-positive and photo-negative vertical movements occurs in the natural environment, these vertical movements, coupled with horizontal transport of larvae by water currents, would provide a search pattern for the host, the diurnally-inactive, bottom-living flatfishSolea solea. When eggs are stimulated to hatch in the chambers with urea, large numbers of larvae emerge within a few min, and it was observed that during the period of about 30 min after stimulation, many larvae are photo-negative. When eggs on the sea bottom are stimulated to hatch by mucus or urine from a nearby host, such behaviour would greatly enhance chances of contact with the fish. When eggs are stimulated to hatch by means of urea in the absence of light, there is evidence that the oncomiracidia are geo-negative. It has been shown that larvae are able to extricate themselves in total darkness from sediment containing buried eggs and that, in an experimental situation illuminated only by an infra-red beam, larvae readily attach themselves to the lower skin of soles within 2 min of hatching. There is evidence that, in aquaria, some invasion of the host takes place from below.
Variable expression of virulence in the rodent malaria parasitePlasmodium yoelii yoelii
Authors: Knowles G. , Walliker D.
Published: June 2009

The expression of the virulence character in the virulent line (YM) ofPlasmodium yoelii yoeliiwas investigated. The level of virulence was measured by counting the parasitaemia of the mature red blood cells. Several sub-clones were isolated from the virulent line YM and each was tested for its level of virulence. Out of 10 sub-clones 1 showed a marked decrease in virulence. However, transmission of this sub-clone through mosquitoes fully restored its virulence. A clone isolated from the progeny of a cross between mild and virulent parents had an intermediate level of virulence. A sub-clone isolated from this intermediate virulent line exhibited greatly reduced virulence. Mosquito transmission of this sub-clone also restored its virulence to a level comparable with the virulent line YM.
A technique using continuous action centrifugation for the quantitative recovery of helminth eggs from vegetation and water
Authors: Storey G. W. , Phillips R. A.
Published: June 2009

A rapid technique for the extraction of helminth eggs from vegetation and water is presented. The technique includes a period of continuous action centrifugation and gives recovery efficiencies of 84 % and 96 % from water and vegetation respectively.
Transmission of Schistosoma mansoni from man to snail: laboratory studies on the influence of snail and miracidial densities on transmission success
Authors: Carter N. P. , Anderson R. M. , Wilson R. A.
Published: June 2009

The relationship between infection success, the density of Schistosoma mansoni miracidia and the density of the snail host Biomphalaria glabrata was examined experimentally. Within laboratory infection arenas, the distribution of miracidial infections/snail was approximately uniform and the net rate of snail infection was directly positive binomial to miracidial density. In contrast, however, the rate of infection declined exponentially as snail density increased. Mathematical models are developed to aid in the estimation of infection rates and experimental results are discussed in the context of the transmission dynamics of schistosomiasis.
The effect of mosquito transmission of antigenic variants ofPlasmodium chabaudi
Authors: McLean S. A. , Phillips R. S. , Pearson C. D. , Walliker D.
Published: June 2009

Plasmodium chabaudiAS strain in mice is characterized by an acute primary parasitaemia, and one or more less acute recrudescences. Previous work has shown, using a passive protection assay, that the recrudescent parasites are usually antigenically different from parasites of the parent population with which the mice were first infected. In this study the effect of mosquito transmission on the antigenic expression of recrudescent populations ofP. chabaudiwas examined. In the first experiments the recrudescent population which was antigenically different from the parent population was uncloned. After transmission throughAnopheles stephensithe recrudescent population appeared to revert to an antigenic type similar to that of the parent population. In the second experiment clones from a recrudescent population were mosquito transmitted and again the parasites of the primary patent parasitaemia in the mice, bitten by the infected mosquitoes, had reverted to the parental type. It is suggested that antigenic variants ofP. chabaudiAS strain may revert to a basic type after mosquito transmission.