The life cycle of Ohbayashinema erbaevae (Nematoda, Heligmosomoidea, Heligmosomidae) in Ochotona rufescens rufescens (Ochotonidae).

The morphogenesis and the chronology of the life cycle of Ohbayashinema erbaevoe Durette-Desset et al, 2000, a parasite of Ochotona daurica from Buriatia were studied in detail in an experimental host, Ochotona rufescens rufescens. Worm-free pikas were each infected per os with O. erbaevae larvae and were killed at one day post infection (DPI 1) and every 12 hours from 1.5 to 8 days post infection. By DPI 1, all the larvae were exsheathed and in the small intestine. The third moult occurred in 2.5-3.0 days. The last moult occurred in 4.0-4.5 days. The prepatent period was eight days and the patent period lasted between two and 12 weeks. The distribution of O. erbaevae along the small intestine of the pikas was assessed. For each experiment, a morphological description of the different stages of the life cycle was provided. The morphogenesis and the chronology of the life cycle of O. erbaevae appear to be identical with those of two other genera of the family of the Heligmosomidae, Heligmosomum Railliet & Henry, 1909 and Heligmosomoides Hall, 1916. They confirm that the three genera belong to the same family. The presence of an abortive posterior genital branch in the female of O. erbaevae, which represents the posterior part of the genital primordium of the didelphic females, supports the systematic position of the genus Ohbayashinema between the didelphic genus Citellinema Hall, 1916 and the monodelphic genera Heligmosomum and Heligmosomoides.

The gametocytes of Plasmodium vinckei petteri, their morphological stages, periodicity and infectivity.

Gametocyte production by P. vinckei petteri was cyclic, occurring at each schizogony every 24 h. They matured in 27 h from merozoite to type 0 microgametocyte, in 3 h from type 0 to type I, 6 h from type I to type II and 3 h from type II to type III. Transmission experiments showed that the time of maximum infectivity was midday when mice were inoculated at midnight, and midnight when mice were inoculated at midday. In all instances, maximum infectivity coincided with a peak in intensity by type II microgametocytes, a relationship confirmed by multiple correspondence analysis. The proportion of type II microgametocytes was higher in the mosquitoes blood meal than in smears of tail blood of mice, suggesting a sequestration phenomenon with this stage.

Antimalarial properties of soy-bean fat emulsions.

Intralipid and Ivelip are commercial preparations of soy-bean lipid extracts used for intravenous supplementation of lipids in various clinical conditions. They were found to inhibit the growth of Plasmodium falciparum in culture with an IC50 of 8.07 +/- 2.13 and 13.32 +/- 2.05 mg.ml-1, respectively. Intralipid rapidly and efficiently inhibited nucleic acid synthesis in cultured P. falciparum, exhibiting full inhibitory activity in less than 2 h. Ivelip injected intraperitoneally, was found by the 4-day suppressive test to be active in vivo against P. vinckei petteri within the normal recommended regimen for dietary lipid supply (0.5-4 g.kg-1), but it was impossible to obtain a radical cure even with very high doses (6.4 g.kg-1). Ivelip was less effective against P. berghei and P. yoelii nigeriensis. As Ivelip showed no interference with the antimalarial activity of chloroquine, it could be considered for use in the treatment of severe human malaria in association with 4-aminoquinolines to expedite the clearance of parasites.

Immunization with the malaria heat shock like protein hsp70-1 enhances transmission to the mosquito.

Mosquitoes fed on mice infected with Plasmodium yoelii after an immunization with the i72 recombinant form of the heat shock protein hsp70-1 developed significantly more oocysts than mosquitoes fed on controls. This effect was due to a marked increase in the relative numbers of gametocytes during the early stages of infection. A comparison of blood-induced and sporozoite-initiated infection showed that these gametocytes were derived from merozoites released from the liver. The stimulus for increased gametocyte production is unknown but is likely to be linked with antibody-dependent cellular cytotoxicity and associated cytokine responses.

The role of reactive nitrogen intermediates in modulation of gametocyte infectivity of rodent malaria parasites.

Direct feeding of Anopheles stephensi mosquitoes on mice infected with Plasmodium vinckei petteri showed that, during the periods of schizogony in the blood, the infectivity of gametocytes was markedly reduced. This could be prevented by prior injection of the L-arginine analogue, Nw-nitro-L-arginine (NwNLA) showing that the altered infectivity was due to reactive nitrogen intermediates (RNI). Similar effects on transmission of P. yoelii nigeriensis were demonstrated in vitro by membrane feeding of the mosquitoes. The in vitro reduction in infectivity could be reversed by injecting the L-arginine analogue either into the infected mouse donor of serum, or into the membrane feeding chamber. Elevated levels of TNF and IL-6 were demonstrated during the course of infection but did not correlate well with nitrogen radical activity. Similarly, direct measurements of NO2- and NO3- did not reflect the nitrogen radical activity revealed by addition of the specific L-arginine analogue.

[Plasmodium vinckei petteri: various aspects of its sporogony and exoerythrocytic schizogony]. / Plasmodium vinckei petteri: algunos aspectos de su esporogonia y esquizogonia exoeritrocitaria.

A study of Plasmodium vinckei peterri sporogony was performed by experimental infection of Anopheles stephensi with gametocytes from infected mice. The study includes the description of the ookinete, complete evolution of oocysts and their final transformation to sporozoites. These were later used for intravenous infection of new mice, in order to study the exoerythrocytic schizogony. The morphology of exoerythrocytic schizonts was similar to that of other species of the same group. The minimal duration of the hepatic cycle was found to be of 61 hours. These data, along with other related to the hematic cycle characteristics, help to complete the information on the species, which can be recommended as a model for the study of human malaria.

Observations ultrastructurales sur les formes sanguines et la sporogonie de plasmodiums de lémuriens malgaches.

The ultrastructure of blood stages and oocysts of Plasmodium coulangesi and P. percygarnhami, both parasites of Madagascan lemurs, was studied. The main results are:

[Plasmodia of lemurs in Madagascar]. / Plasmodies de lémuriens malgaches.

Lemur macaco macaco from Ambanja region was found polyparasitized by four different species of Plasmodium: --Plasmodium coulangesi recently described by lepers et al. (1989). --P. bucki n. sp.: its main differential characterisitics are the large numvber (32) of merozoites produced in mature schizonts and the stippling, resembling Maurer's dots, in an hypertrophied pinkish erythrocyte. --P. percygarnhami n. sp. (= P. girardi sensu Uilenberg, 1970 pro parte and sensu Garnham et Uilenberg, 1975 pro parte) producing 20 merozoites in mature schizonts and developing inside a deformed corpuscle (holly leaf-shaped or sometimes sea-urchin-shaped) which may also become decolourized when parasitized by older stages. --(?) Plasmodium lemuris: gametocytes are very large (11 microns x 7 micron); the parasitized erythrocyte is much hypertrophied (+/- 10 microns), distored and of a pinkish colour; one schizont only, possibly exo-erythrocytic, was found. The authors hypothesized this parasite to be a Haemoproteid. The analysis of published data led the authors to make the following modifications to the nomenclature previously established: --Plasmodium girardi Buck et al., 1952, sensu Garnham, 1966, sensu Uilenberg, 1970 parte and sensu Garnham and Uilenberg, 1975 pro parte, is refered to as Plasmodium sp., for stages developing in the blood of Lemur fulvus fulvus. The taxon P. percygarnhami is to be employed for stages developing in L. m. macaco and P. girardi Buck et al., 1952 for those developing in Lemur fulvus rufus. --Plasmodium foleyi Buck et al., 1952, sensu Garnham and Uilenberg, 1975 in L. f. fulvus is named Plasmodium uilenbergi n. sp., P. folleyi being a parasite of L.f. rufus. Excluding P. lemuris which probably does not belong to the genus Plasmodium, the morphological analysis led to individualize 7 species, in the three species of Lemurs studied. A phenomenon of "vicariance" thus appears, similar to what is known for the african Rodent Plasmodia, but with a more pronounced speciation. The vicariant species form a pair constituted of: --on the one hand a small species developing in a red blood cell of normal size, P. girardi in L.f. rufus, P. sp. in L.f. fulvus, P. percygarnhami, with also, P. coulangesi, in L. m. macaco; --on the other hand a large species determining an hypertrophy of the erythrocyte, P. foleyi in L.f. rufus, P. uilenbergi in L.f. fulvus and P. bucki in L.m. macaco.

[Trypanosomes of Estrildidae birds. II. Biological studies]. / Sur les trypanosomes d'oiseaux Estrildidae. II--Etudes biologiques.

Studies on the biology of 4 Trypanosomes of Estrildidae birds described in a previous paper (Chandenier et al., 1988) are related. In Culicoides nubeculosus, the complete development is achieved in 7 days. After a phase of intense multiplication of amastigotes in the gut, infective trypomastigotes appear. In cultures, infective stages are obtained in 13 days. Transmission to clean birds was attempted: in two out of 8 attempts, a satisfactory level of parasitaemia is obtained. Surprisingly Trypanosomes infecting the new birds are unable to develop further in cultures or in Culicoides. The most likely hypothesis is the lack of a factor allowing the Trypanosomes to mature.

[The trypanosomes of birds of the family Estrildidae. I. Morphologic and systematic study]. / Sur les Trypanosomes d'oiseaux Estrildidae. I--Etude morphologique et systématique.

Twenty two birds belonging to the species Estrilda melpoda and E. astrild were studied. Nine birds were found infected by Trypanosomes. They belong to four different species: one is identified as Trypanosoma everetti, the other three are new species (T. chabaudi, T. davidmolyneuxi and T. gentilinii). Several mixed infections were found. Each species appears to be monomorphic in the circulating blood; it is suggested that the polymorphism of several Trypanosomes described in the literature is due to polyparasitic infections rather than to a true polymorphism.

Experimental modifications of the circadian rythm of Plasmodium vinckei petteri following cryopreservation; probable resistance of the merozoïte to thawing.

Plasmodium vinckei petteri, in white mice, is a particularly useful strain for studies on the circadian rythm of Plasmodium. An experimental model was set up: it showed that the rythm of asexual schizogony in the blood varies with the time and the mode of inoculation (cryopreserved blood or syringe passage). When frozen blood is injected, the time of schizogony depends on the time of injection; on the contrary, when the passage is by syringe from mouse to mouse, the rythm of schizogony is the same in the donor and the receptor mouse, regardless of the time of injection. The only possible explanation is that all intracellular parasites are destroyed by the thawing of blood and the free merozoïte is the only resistant stage.

Effect of cholesterol-rich diet on the susceptibility of rodent malarial parasites to chloroquine chemotherapy.

Mice were fed a cholesterol-rich diet and then subsequently infected with chloroquine-sensitive strains of either Plasmodium berghei or P. chabaudi. Chloroquine therapy, which was started 24 hours post-infection and continued for 3-4 days, was significantly less effective in cholesterol-fed animals compared to controls. The consequences of these findings to the resistance of P. falciparum in man to chloroquine, are discussed.

[Ultrastructure of chronic reticuloendothelial forms of Isospora of sparrows]. / Ultrastructure des formes chroniques réticulo-endothéliales des Isospora du moineau.

Mononucleated reticulo-endothelial stages of Isospora from Sparrows were studied by T. E. M. during the winter period when the extra intestinal infection is chronic. Results show a very slow evolution from merozoite to trophozoite stage, a transformation of the parasite nucleus and a characteristic reaction of the host cell. These observations are discussed in relation to what is known of hypnozoite and chronic schizogony of Plasmodium.

[Inhibition of the infectivity of Plasmodium gametocytes by the serum of the parasite host. Perfecting an experimental model]. / Inhibition de l'infectivité des gamétocytes de Plasmodium par le sérum de l'hôte parasité. Mise au point d'un modèle expérimental.

In the course of experimental malarial infections the infectivity of the gametocytes falls abruptly and at an early stage of the infection. This phenomenon is independent of the production of circulating antibodies. With Plasmodium yoelii nigeriensis infecting the white mouse, the maximum infectivity of gametocytes for Anopheles stephensi occurs on day 2, and on day 5 no more oocysts develop in the mosquito. The behaviour of the plasmodial strain in the mouse and particularly the "crisis" phenomenon were studied in detail in standardized experimental conditions. The decrease of the infectivity for the Anopheles begins just before the peak of parasitaemia, and a concomitant increase in the number of circulating gametocytes is observed. These events are very shortly followed by the crisis. The more severe is the crisis and virulent the infection, the earlier and more abrupt is the loss of infectivity. Previous studies having shown that this inhibition of the gametocytes infectivity was linked to a serum factor, our research aimed at setting up an experimental model allowing the identification of this factor. The intravenous injection of 5th day serum to mice harbouring infective gametocytes did not determine any loss of the gametocytes infectivity in the receiving mice. In order to study in vitro the effect of the 5th day serum, this one was added to blood from mice with highly infective gametocytes, and mosquitoes were fed on this through a membrane. As a result, a significant decrease of the infectivity of gametocytes was observed. This inhibition is immediate and does not appear to be "dose-dependent". Inversely, serum from mice still infective to the mosquito did not reduce the infectivity of the gametocytes. The experimental model set up thus comprises: a) mouse blood containing P. y. nigeriensis infective gametocytes to which is added the serum to be tested; b) Anopheles stephensi fed through a membrane; this allows quantifying the infectivity of the gametocytes in the presence of normal serum (control) or inhibitory serum. This model proved to be reliable; it should promote the study of any factor likely to modify the infectivity of Plasmodium gametocytes to the mosquito.

Fractionation of mouse malarious blood according to parasite developmental stage, using a Percoll-sorbitol gradient.

Asexual intraerythrocytic malarial parasites permeabilize the membrane of their host cell to small monelectrolytes and anions. Since permeabilization increases with parasite maturation, this property has been used previously to fractionate blood infected with Plasmodium falciparum and P. knowlesi according to the developmental stage of the parasite, using Percoll-sorbitol density gradients. We have extended this method to fractionate mouse blood infected with four species of rodent malaria: P. chahaudi, P. vinckei, P. voelii and P. berghei. While the method works in principle in this case, the polyparasitism which characterizes these species prevented explicit separation according to developmental stage. Hence, erythrocytes harbouring several ring-stage parasites appeared in the same fraction which contained cells hosting a single trophozoite, and polyparasitized trophozoites were associated with singly-infected schizont. This observation implies that permeabilization of the host cell membrane results from the integrated metabolic activity of the parasite(s) and is not related to a specific phase of parasite development.

[Ultrastructural observations on the blood stages of Garniidae (G. gonatodi G. uranoscodoni and Fallisia effusa) parasites of South American Lizards)]. / Observations ultrastructurales sur les formes sanguines des Garniidés (Garnia gonatodi, G. uranoscodoni et Fallisia effusa) parasites de lézards sud-américains.

The ultrastructural study of two species of Garnia (G. gonatodi and G. uranoscodoni) and of Fallisia effusa demonstrates that the Garniidae possess the fundamental structures of Haemosporidia. A vacuolar digestive system was not found and the absence of pigment granules is confirmed. A number of caracteristics (- centriolar plaque inside a nuclear pore; - highly developed cytosqueleton in the host cell of F. effusa; - advanced maturation stages of gamétocytes of F. effusa in the vertebrate host) allow comparisons between the Garniidae and Plasmodiidae, Leucocytozoidae and Haemoproteidae. The authors' conclusion is that Garnia and Fallisia, although clearly different from each other, have common ultrastructural characteristics which also separate them from the other Haemosporidian families.

Ultrastructural studies of alterations induced by microwaves in Toxocara canis eggs: prophylactic interest.

The ultrastructure of Toxocara canis eggs is described before and after exposure to microwaves. The morphology of normal eggs is compared to that of eggs from other helminths. Following treatment, the complete disorganization of the surface structure of the shell and the loss of much turgidity of the egg are observed. The destruction of the internal structure is most marked in the center of the egg and is associated with the disappearance of some layers of the shell. In addition, there is substantial damage to the synthesis apparatus (ribosomes, endoplasmic reticulum, lipid cisternae). An explanation based on the specific action of microwaves and micro-overheating is proposed, and the prophylactic use of this technique is considered.

[Cultivation of exo-erythrocytic schizonts of rodent Plasmodium in hepatocytes: a new experimental model for chemotherapy of malaria]. / La culture des schizontes exo-érythocytaires des Plasmodium de rongeurs dans des hépatocytes: un nouveau modèle expérimental pour la chimiothérapie du paludisme.

An in vitro experimental model using primary cultures of laboratory bred Thamnomys gazellae's hepatocytes and Plasmodium yoelii yoelii' sporozoites was set up for chemotherapeutic studies. The surface of the culture was reduced (0.5 cm) and allowed the rapid performance and analysis of schizonticide activity tests, with a reduced biological material (Rodents, Anopheles, sporozoites). Fifteen compounds were tested. When activity of molecules is known in vivo, both results in vivo and in vitro are parallel.