The time and Site of expression of five antigens, recognized by monoclonal antibodies raised against blood-stage parasites, were studied in the exoerythrocytic stage of Plasmodium berghei using indirect immunofluorescent antibody staining. Two monoclonal antibodies (W 3. 5, I 2. 6), which stain the cytoplasm of infected erythrocytes, did not stain the cytoplasm of the infected liver cell but stained the parasite itself suggesting a difference in the antigenic architecture of the erythrocytic and exoerythrocytic parasites. Another antibody (17. 6. 1) revealed a further difference in the antigenic composition of the blood and liver-stage parasites being expressed almost exclusively in the former. Two others (C139 and 17. 3. 9) showed broadly similar patterns of expression in these two stages of the malarial life-cycle.

The use of an electrically driven Sharples super-centrifuge for isolating viruses is described. The theory of sedimentation in such centrifuges is discussed and curves of the theoretical minimum sedimentation rates are given. The probability that convectionless sedimentation cannot take place in high-speed preparative centrifuges is discussed in relation to the theory of ‘differential centrifugation’.

In the present study ultrastructural immunocytochemical techniques have been used to localize the cells producing two soluble egg antigens present in the hatching fluid of Schistosoma mansoni, using two recently described monoclonal antibodies (MAbs). In the miracidium of S. mansoni, the one apical and the two lateral unicellular glands showed immunoreactivity for the egg antigens, using a post-embedding immunogold technique. Immunoreactivity was associated with the contents of vesicles for both the MAbs, although the intravesicular distribution was not identical. This difference in ultrastructural staining pattern provides additional evidence that the two MAbs are binding with different epitopes of the same antigen or with different antigens altogether. The finding of free unbound label around the embedded miracidium is consistent with secretion having been released from the glands.

1. Worms which had been cultured in media of different osmotic pressures were immersed in concentrated solutions of NaCl, KC1, CaCl2 and MgCl2, and the times of cessation of spontaneous movement noted.

2. Worms from ‘normal’ cultures were immersed in a single concentration of each of the above solutions (all osmotically equivalent to 0·51 M NaCl) and the shrinkage curves were determined.

3. Worms from ‘normal’ cultures were placed in NaCN and KCN solutions and the subsequent shrinkage on immersion in a concentrated balanced salt solution was measured. From these results it is concluded that cyanide decreases the permeability of the body to water, and also that NaCN enters the body more rapidly than KCN.

4. It has been shown that the chloride solutions which produce the greatest effect on the movement of the worms produce the least shrinkage and vice versa. From this it is concluded that the substances investigated can be arranged in order of their rates of penetration approximately as follows: NaCl> CaCl2> MgCl2, KCl.

5. It is suggested that the results obtained are more easily explained on the assumption that the rates of penetration of the substances used are controlled by the activities of living protoplasm than by the properties of non-living cuticle.

Insect parasitic nematodes have acquired mechanisms to evade their host immune response for successful parasitism. Despite the importance of understanding of the evolution of evasion mechanisms from host immunity, insect immune response against non-parasitic nematodes has not been well studied. In our previous study, we demonstrated that a non-insect parasitic nematode Caenorhabditis elegans was not encapsulated by haemocytes in the larvae of the greater wax moth Galleria mellonella. To understand how nematodes influence insect haemocytes to escape encapsulation, we examined the effect of C. elegans on haemocytes in the haemocoel of G. mellonella larvae. Injection of nematodes resulted in the decrease of haemocyte density while mortality and spreading ability of haemocytes, the haematopoietic organs were not affected. In vitro co-incubation of haemocytes with nematodes resulted in a decrease of haemocyte density and we observed feeding on haemocytes by nematodes. Injection of C. elegans feeding-delay mutants into insects did not cause the decrease of haemocyte density. The decrease of haemocyte density was due to the nematode's ingestion of haemocytes. Furthermore, an entomopathogenic nematode and other bacterial feeding nematodes also showed similar feeding behaviour. The nematode's ability to feed on haemocytes may have played an important role in the evolution of nematode parasitism in bacterial-feeding nematodes.

The isolation and molecular characterization of the gene coding for L14 ribosomal protein from L. braziliensis is described. There are 2 copies of the gene per haploid genome, repeated in a head-to-tail tandem orientation and located in a single chromosome of approximately 950 kb. Northern blot analyses indicate the presence of a single transcript of 0·95 kb which is up-regulated when parasites reach the stationary growth phase. L. braziliensis L14 gene codes for a 175 amino acid long polypeptide showing 75–83% sequence identity with L14 proteins from trypanosomatids and approximately 25% with its counterparts from higher eukaryotic organisms. L14 ribosomal proteins from trypanosomatids and higher eukaryotes share along their molecules a similar distribution pattern of theoretically functional domains. L. braziliensis L14 recombinant protein is not recognized by sera from cutaneous leishmaniasis patients. Immunization of mice with one dose of L14 recombinant protein and a second dose of L14 protein covalently linked to the HSP70 from Trypanosoma cruzi induces a high antibody level against this L14 protein, which is mostly of the IgG2a subtype, as well as a strong increase in splenocyte proliferation index.

Aragão (1912) has recently described a new species of tick which he raised through three complete generations upon cold-blooded animals, the natural hosts in Brazil. He gave the species the name Amblyomma agamum because reproduction occurred parthenogenetically, males not having as yet been observed. The tick, in common with most other Ixodidae, feeds upon three successive hosts in the larval, nymphal and adult stages; it may, however, undergo metamorphosis from larva to nymph upon the host. This observation of Aragão's is the first of the kind, for parthenogenesis has not hitherto been observed in ticks. In the course of his raising experiments he obtained thousands of females which laid fertile eggs in the absence of males.

The object of this paper is the description of a dipterous larva based on the study of six specimens of larvae obtained by Mr R. A. Phillips from living specimens of the snail Vertigo genesii Gredler which he had caught at Cloanascragh Bog, near Taum, Co. Galway. Three larvae were received in October 1933 through Prof. Boycott, and three in September 1936 directly from Mr Phillips. In a letter accompanying the specimens Prof. Boycott makes the following remark:

“Considering that the whole snail shell is only about 2 mm. × 1 mm. the larvae seem very big.” In fact some of the shells are distinctly smaller than the adult larvae, which when mounted are 2·0–5·0 mm. long, and 0·3–1·5 mm. in diameter.

(A) Life History.

(1) Simulium larvae are found in streams where the current is very fast. They are sedentary in habit and fix themselves to some support by means of their posterior sucker and sticky salivary secretion.

(2) Progression is achieved by looping movements which have been described in detail.

(3) Larvae feed on all kinds of fresh water animalcules, and algae.

(4) Two species were reared from eggs to the adult flies for the first time in the laboratory. Abundance of food and aeration of water are two very important factors governing the rearing of these larvae.

(5) There are six larval stages, each stage lasting 4–7 days. The gradual changes in the successive stages are described in S. erythrocephalum and S. aureum.

(6) The sixth-stage larva, having woven its cocoon, changes into a pupa, the whole process, weaving of cocoon and pupation (described in detail), takes 75–90 minutes. Pupal life lasts 5–15 days, depending on temperature.

(7) The eggs are sub-triangular in form and are laid in large patches on aquatic plants below the surface of water.

(8) The first-stage larva is characterised by the presence of an egg-burster situated dorsally upon the head.

(B) Morphology.

(9) The larvae are eucephalous, with eleven faintly marked body-segments, three thoracic and eight abdominal, the eighth abdominal being apparently divided into two parts, the posterior carrying the anus and posterior sucker. There is a median uniramous thoracic proleg which like the posterior sucker is provided with a number of cuticular hooks.

(10) The head has a number of markings which are of great taxonomic importance.

(11) The head-appendages are: A pair of jointed antennae, a rounded labrum, a pair of lateral fan-shaped appendages (the premandibular organs), a pair of mandibles, a pair of maxillae each with a single-jointed palp, a hypopharynx, and a labium. These appendages have been described in detail in this paper for the first time.

(12) The alimentary canal, malpighian tubules, salivary glands, muscular system and gonads are dealt with in detail.

(13) The oesophageal valve has no blood sinus as has been erroneously described by previous writers.

(14) A pair of dorsal glands are present above the pharynx. Their walls consist of large uninuclear cells. Dorsal glands have so far been found only in Sciara among Dipterous larvae.

(15) There is a well-developed central as well as visceral nervous system. The bilobed brain lies in the head and a chain of eleven ganglia in the body. Both the supra-intestinal and the infra-intestinal visceral systems are fully worked out for the first time.

(16) There is a well-developed tracheal system with ten closed spiracles, one prothoracic, one metathoracic and eight abdominal.

(17) The flattened dorsal vessel stretches from the seventh abdominal segment to the head where it ends just behind the brain. It is dilated in the seventh segment to form the heart which is provided with two pairs of ostia.

(18) Nephrocytes or excretory cells (pericardial, and peri-oesophageal) are described for the first time and compared to similar structures in other Dipterous larvae.

(19) A detailed description of the early stages of all the known (seventeen)1 British species is given, with remarks about eleven of them, as they occur in Sweden, Norway and France.

(20) The characters used for determining the species are as follows: Larva. Head markings; antennae; mandibles; submentum; anal gills; ventral papillae; and posterior sucker. Pupa. Chaetotaxy, Respiratory filaments, and Cocoon.

Dans un travail publié précédemment dans cette revue, nous avons montré que la concentration moléculaire du liquids cœlomique d'Ascaris megalocephala était voisine de Δ = − 0°, 63 avec de petites variations; d'après nos expériences, l'Ascaris était susceptible d'une régulation osmotique; il augmente de poids dans une solution hypotonique par rapport à son liquide; il y a pénétration d'eau; dans une solution hypertonique il diminue de poids (départ d'eau).

Seroprevalence data illustrate that human exposure to Toxocara is frequent. Environmental contamination with Toxocara spp. eggs is assumed to be the best indicator of human exposure, but increased risk of exposure has also been associated with many other factors. Reported associations are inconsistent, however, and there is still ambiguity regarding the factors driving the onset of Toxocara antibody positivity. The objective of this work was to assess the validity of our current conceptual understanding of the key processes driving human exposure to Toxocara. We constructed an agent-based model predicting Toxocara antibody positivity (as a measure of exposure) in children. Exposure was assumed to depend on the joint probability of 3 parameters: (1) environmental contamination with Toxocara spp. eggs, (2) larvation of these eggs and (3) the age-related contact with these eggs. This joint probability was linked to processes of acquired humoral immunity, influencing the rate of antibody seroreversion. The results of the simulation were validated against published data from 5 different geographical settings. Using simple rules and a stochastic approach with parameter estimates derived from the respective contexts, plausible serological patterns emerged from the model in nearly all settings. Our approach leads to novel insights in the transmission dynamics of Toxocara.

We address the question of whether host and/or environmental factors might affect endoparasite richness and distribution, using carnivores as a model. We reviewed studies published in international peer-reviewed journals (34 areas in the Iberian Peninsula), describing parasite prevalence and richness in carnivores, and collected information on site location, host bio-ecology, climate and detected taxa (Helminths, Protozoa and Mycobacterium spp.). Three hypotheses were tested (i) host based, (ii) environmentally based, and (iii) hybrid (combination of environmental and host). Multicollinearity reduced candidate variable number for modelling to 5: host weight, phylogenetic independent contrasts (host weight), mean annual temperature, host trophic level and biogeographical region. General Linear Mixed Modelling was used and the best model was a hybrid model that included biogeographical region and host trophic level. Results revealed that endoparasite richness is higher in Mediterranean areas, especially for the top predators. We suggest that the detected parasites may benefit from mild environmental conditions that occur in southern regions. Top predators have larger home ranges and are likely to be subjected to cascading effects throughout the food web, resulting in more infestation opportunities and potentially higher endoparasite richness. This study suggests that richness may be more affected by historical and regional processes (including climate) than by host ecological processes.

Lobochona insularum sp.nov., a collar ciliate (Chonotrichida), an ectocommensal on the pleopodal bristles of a gribble from Hawaii, is described. L. insularum differs from the previously described chonotrichidan ectocommensals of the gribbles, L. limnoriae on Limnoria lignorum and Lobochona prorates on Limnoria tripunctata, in the outlines of the body and of the marginal lappets of the collar.

This work was supported by a grant from the National Science Foundation. Various facilities were made available by the Allan Hancock Foundation of the University of Southern California.

Acknowledgement is given to Dr Bayard H. McConnaughey, who discovered the organism and prepared the slides.

Evidence is presented of a periodicity of oogenesis and spermatogenesis in D. aegira. Pauses in oogenesis were detected between successions of oogonial divisions; in spermatogenesis, the intervals appeared to be longer and the pauses came before division of primary spermatocytes. Regulation of division rates was such that between two and three times as many spermatozoa as oocytes were produced.

Observations indicated that spermatozoa emerged from the axial cell soon after their formation and made contact with oocytes early, often before these were fully grown. Properties of the oocyte cell membrane evidently precluded precocious sperm entry and the penetration of more than one spermatozoon.

Sincere thanks are due to Dr R. B. Short, who kindly made available all the material, and to Dr S. W. Fox and Dr C. B. Metz for the excellent facilities provided. This work was supported by P. H. S. Research Grant E 4749 (Institute of Allergy and Infectious Diseases) awarded to R. B. Short, and by N.A.S.A. Grant NsG–173–62 and N.S.F. Grant G–9150. Contribution No. 019 of the Institute for Space Biosciences.

The biochemical constitution of the copepod parasite Mytilicola intestinalis was determined and seasonal changes were detected which, in general, could be correlated with the life-history of the parasite.

Biochemical constituents have been discussed in relation to those in other endoparasites and free-living crustaceans. It was concluded that carbohydrates and lipids both formed important stores of energy in M. intestinalis. Protein levels were reduced compared with those in free-living forms.

This work forms part of a Ph.D. thesis in the University of London. It was completed during the tenure of a Research Assistantship at The Polytechnic, Regent Street, London W. 1.

It was found that antelopes in the Serengeti area, Tanzania, East Africa, are heavily infested with lung nematodes. Five species of the family Protostrongylidae, namely, Protostrongylus africanus sp.nov., P. etoshai Ortlepp, P. gazellae Yeh, Pneumostrongylus calcaratus Mönnig and P. cornigerus Ortlepp, as well as one species of the family Dictyocaulidae, Dictycaulus viviparus (Bloch), were recorded.

A detailed description of Protostrongylus africanus sp.nov., which is conspicuous for its gigantic size, is given, and the lesions caused by this lung nematode are described.

The distribution and incidence of lung nematodes in the various antelope species are discussed.

The parthenogenetic metacercarial stages of the gymnophallid trematode Cercaria margaritensis are found in the extrapallial cavity of the subtidal prosobranch mollusc Margarites helicinus. The primary metacercariae (M1) produce second-generation metacercariae (M2) which become independent and give rise to M3 metacercariae which are infective to the definitive host, the common eider (Somateria mollissima). This study used transmission electron microscopy to follow the development of M2 inside M1 organisms and M3 inside M2 organisms. The process is similar in both cases with embryos developing from individual cells from the parent body walls. In each case the brood sac was divided into brood chambers by multilaminated cells and both M2 and M3 embryos developed inside embryonic membranes that originated from specialized blastomeres. The tegument of M2 and M3 embryos developed in a similar manner underneath the embryonic membrane. Both the multilaminated cells and the embryonic membranes possessed features that indicated that they are involved in transport of nutrients. It is suggested that the continuous nature of M2 and M3 embryo development may well be similar to that postulated for ancestral digeneans.

The lateral diffusion (DL) properties of the fluorescent lipid probe 5-N (octadecanoyl) aminofluorescein (AF18) inserted into the surface of muscle-stage larvae of Trichinella spiralis were investigated by fluorescence recovery after photobleaching. AF18 was not free to diffuse laterally in dormant larvae, and this remained unchanged after larval activation in vitro with trypsin and bile. However, a significant increase in surface fluidity of the probe was demonstrated (%R = 74·5; DL = 11·5 × 10−9 cm2/sec) when larvae invaded intestinal epithelial tissue following oral infection of mice. Membrane-permeant photoactivatable caged cyclic AMP was used to analyse the putative mechanism responsible for this increase in lateral diffusion in the parasite surface. Although incubation of larvae with 1–50 μM caged cAMP had no effect on surface fluidity, incubation with 100 μM caged cAMP induced a substantial increase in the lateral mobility of AF18 (%R = 64·3; DL = 8·3 × 10−11 cm2/sec) immediately following photo-activation of the caged messenger. This induced fluidity, however, was transient and the larval surface reverted to immobility within 15 min. These observations constitute the first reported measurement of the fluid properties of the surface of intracellular parasites, the first demonstration of the parasite surface fluidity altering as a result of host cell invasion and the first indication of a mechanism underlying changes in surface fluidity in parasitic helminths.

Immunoactivation depends upon the antigen potential to modulate T-cell repertoires. The present study has enumerated the effect of 61 kDa recombinant Leishmania donovani co-factor-independent phosphoglycerate mutase (rLd-iPGAM) on mononuclear cells of healthy and treated visceral leishmaniasis subjects as well as on THP-1 cell line. rLd-iPGAM stimulation induced higher expression of interleukin-1β (IL-1β) in the phagocytic cell, its receptor and CD69 on T-cell subsets. These cellular activations resulted in upregulation of host-protective cytokines IL-2, IL-12, IL-17, tumour necrosis factor-α and interferon-γ, and downregulation of IL-4, IL-10 and tumour growth factor-β. This immune polarization was also evidenced by upregulation of nuclear factor-κ light-chain enhancer of activated B cells p50 and regulated expression of suppressor of mother against decapentaplegic protein-4. rLd-iPGAM stimulation also promoted lymphocyte proliferation and boosted the leishmaniacidal activity of macrophages by upregulating reactive oxygen species. It also induced 1·8-fold higher release of nitric oxide (NO) by promoting the transcription of inducible nitric oxide synthase gene. Besides, in silico analysis suggested the presence of major histocompatibility complex class I and II restricted epitopes, which can proficiently trigger CD8+ and CD4+ cells, respectively. This study reports rLd-iPGAM as an effective immunoprophylactic agent, which can be used in future vaccine design.

Prior to 1939 our knowledge of the mites of the sub-family Trombiculinae was limited to about a dozen species, whose life history had been the subject of investigations by Nagayo and his associates in Japan, Walch in the Dutch East Indies and Gater, Fletcher, Lesslar and Lewthwaite in Malaya.