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Biomedical subjects

A G Chabaud

Publications and source records attributed to A G Chabaud.

At least 37 records · Page 2Linked to original sources
PubMed1995

Plasmodium vinckei vinckei and P. yoelii nigeriensis: pattern of gametocyte production and development.

The morphological evolution and the periodicity of the gametocytes of two rodent malaria species were studied in the white mouse. Experiments with Plasmodium vinckei vinckei, a highly synchronous species, showed that the production of the sexual stages was periodic and was set by the specific rhythm of the asexual stages, i.e. the time of inoculation and the duration of the cycle in the blood. The duration of gametocytogenesis from merozoite to stage 0 was approximately 30 hours, and from stage 0 to stage III, 6 hours. Plasmodium yoelii nigeriensis which normally develops asynchronously in the blood was synchronized by a Percoll-glucose gradient fractionation. Although the duration of the asexual cycle was 18 hours, gametocytogenesis from merozoite to stage 0 lasted 24 hours and 12 hours from stage 0 to stage III. Some degree of sequestration was observed in the young gametocytes.

Animals↗
PubMed1994

Synchronization of Plasmodium yoelii nigeriensis and P. y. killicki infection in the mouse by means of Percoll-glucose gradient stage fractionation: determination of the duration of the schizogonic cycle.

The youngest (rings and young trophozoites) erythrocytic stages of Plasmodium yoelii nigeriensis and P. yoelii killicki, two rodent malaria subspecies developing very asynchronously in the blood, were separated from the other stages using a discontinuous Percoll-glucose gradient. They were inoculated into mice and the subsequent infection remained synchronous for two generations. The duration of the asexual cycle was found to be 18 h.

Animals↗
PubMed1994

The chemosensitivity of the rodent malarias--relationships with the biology of merozoites.

According to the hypothesis proposed by Landau, Cambie & Chabaud (1990, Annalees de Parasitologie Humaine et Comparée 65: 101-103), the chemoresistance of malaria is related to the selection of strains with latent merozoites, the latter being capable of penetrating into red blood cells at other times than that of the time of schizogony and reinfect the host with as much of a delay as several days. They determine an asynchronism of the schizogonic rhythm and, being so far resistant to all known medication, should induce, at least to some extent, a chemoresistance. Consequently, there are three factors linked to merozoites: latency, asynchronism and chemoresistance. The relationship between asynchronism and latency of merozoites has been demonstrated previously (Cambie, Landau & Chabaud, 1990, Compte Rendus de l'Academie des Sciences de Paris 310: 183-188.). In the present work it was shown that the two classifications of strains, first in order of increasing chloroquine resistance, second in order of increasing degree of persistance of merozoites in the blood, are almost identical for the 10 strains, subspecies or species of Plasmodium considered. The relationship between latency of merozoites and chemoresistance appears to have been demonstrated.

Animals↗
PubMed1994

The evolutionary expansion of the Spirurida.

The possible origins of the 12 superfamilies of the Spirurida are considered, based on comparative morphology, host and geographic distributions. The available evidence suggests a complex origin of these nematodes, some families being derived from the Seuratoidea, and others from the Cosmocercoidea (Ascaridida). The spirurid radiation is an old one and seems to have occurred primarily in the Secondary or early Tertiary eras. Since then, expansion has occurred with host capture as a prominent mechanism. The Dracunculoidea Procamallanidae and Camallanidae are probably derived from the Chitwoodchabaudiidae and the Rictularioidea from the Schneidernematidae. The Seuratidae may have given rise to the Gnathostomatoidea, the Physalopteroidea, the Thelazioidea, the Habronematoidea, the Spiruroidea and the Acuarioidea. The filarioid nematodes appear to have several origins with the Diplotriaenoidea derived from the Spiruroidea, while constituents of the Aproctoidea derived from the Cystidicolinae, the Seuratoidea and the Spiruroidea. The Filarioidea are thought to have arisen from the Spiruroidea and the Thelazioidea. The evolution of tissue parasitism as a secondary phenomenon is considered in various groups.

Adaptation, Biological↗
PubMed1994

Latency of Plasmodium merozoites and drug-resistance. A review.

The authors summarize the results of recent work evidencing the existence of latent merozoites during the course of the erythrocytic cycle of the rodent Plasmodia. These merozoites, unlike the majority of merozoites released at schizogony, do not penetrate immediately into the erythrocytes and remain latent for a variable length of time. The merozoites of each of the species or subspecies show marked peculiarities which are responsible for the characteristics of their cycle. The presence of latent merozoites free in the blood, the asynchronous development, and the resistance to chloroquine, are three closely related factors. Knowing that the merozoite is so far drug resistant, and that latent merozoites can maintain the infection for any length of time, it appears important to take into account these purely biological data, when studying the drug resistance of the human falciparum malaria.

Animals↗
PubMed1994

Plasmodium yoelii nigeriensis: biological mechanisms of resistance to chloroquine.

The sensitivity to chloroquine according to the degree of synchronicity of Plasmodium yoelii nigeriensis, which is considered to be the most resistant of the rodent malaria strains, was studied. The infection was synchronised by means of a Percoll-glucose gradient which separates rings and young trophozoites from other stages. The mid-term trophozoite, when it predominated in the blood at the time of treatment, was shown to be as sensitive to chloroquine as Plasmodium vinckei petteri. According to previous results indicating that part of the population of merozoites is latent and penetrates around midnight, the inoculations were timed in order to obtain a lower or higher degree of synchronisation. The infection appeared to be better synchronised if rings and young trophozoites, were inoculated at 06:00 hrs rather than at 15:00 hrs and consequently the efficacy of chloroquine was higher in the former than in the latter.

Animals↗
PubMed1994

Plasmodium vinckei vinckei, P. v. lentum and P. yoelii yoelii: chronobiology of the asexual cycle in the blood.

The biological rhythms of Plasmodium vinckei vinckei, P. v. lentum and P. yoelii yoelii i.e. synchronicity, duration of the erythrocytic cycle, timing of the schizogony and of the penetration of merozoites into red blood cells, were studied in the Swiss white mouse. Two different methods of synchronisation were used: the freezing-thawing of parasitized blood and the inoculation of a single parasitic stage, separated from the other stages by centrifugation through a Percoll-Glucose gradient. The duration of the schizogonic cycle of P. v. vinckei and P. v. lentum, two highly synchronous subspecies, was 24 hours. With P. v. vinckei the timing of the schizogony was independent of the circadian rhythm of the host and was set by the time of inoculation. With P. v. lentum the timing of the schizogony and merozoites penetration into red blood cells depended both, on the hosts rhythm and the time of inoculation of frozen-thawed blood: schizogony occurred at 18:00 if the inoculum was injected at 06:00 or 12:00 and at 06:00 if injected at 18:00 or 00:01. P. y. yoelii a naturally asynchronous parasite was synchronized by means of a Percoll-Glucose gradient. The duration of its intraerythrocytic cycle was found to be 18 hours, similar to that of the other subspecies of P. yoelii.

Animals↗
PubMed1993

On an infection of a human eye with Parastrongylus (= Angiostrongylus) sp. in Sri Lanka.

A metastrongyle worm extracted from the anterior chamber of the right eye of a patient in Sri Lanka belongs to the genus Parastrongylus and probably to a yet undescribed species, related to P. cantonensis well known to infect man. It is mostly a parasite of rodents, wandering in man and unadapted to this host. Evidence for this lack of adaptation are that the specimen is undergoing necrosis (teratological specimen) and is located in an organ with little immunological defences.

Adult↗
PubMed1993

[Nomenclature of Strongylidae above the family group].

It is necessary to distinguish the three main evolutionary lines which presently constitute the Trichostrongyloidea. We propose to raise the following taxa of Strongylida as presented in the CIH keys (1974). Ancylostomatina for Diaphanocephaloidea and Ancylostomatoidea. Strongylina for Strongyloidea. Trichostrongylina for Trichostrongyloidea. Metastrongylina for Metastrongyloidea. The Trichostronglyina suborder includes three superfamilies: Trichostrongyloidea, Molineoidea superfam. nov. and Heligmosomoidea superfam. nov.

Animals↗
PubMed1992

Plasmodium vinckei petteri: identification of the stages sensitive to arteether.

Antimalarial activity of arteether, a derivative of artemisinin (qinghaosu) against blood-induced infections of the highly synchronous Plasmodium vinckei petteri rodent species of malaria was evaluated in Swiss mice. A single subcurative dose of arteether of 2.2 mg/kg body weight was injected subcutaneously to mice, either during the prepatent period or during the patent infection, when different stages of the parasitic cycle were present in the blood. It was shown that rings and young trophozoites were the most susceptible stages to arteether. The drug had no effect on merozoites and little effect on mid-term trophozoites which is the stage most sensitive to chloroquine. The alcoholic solution (10% alcohol in sterile water) had an immediate effect while the oily solution (miglyol 840) was active between 3 and 21 hr after injection.

Animals↗
PubMed1991

Taxonomy, evolution and life cycles.

Three lectures were given, the first on haplodiploidy in the Oxyurida (Nematoda), the second on rodent Oxyurida and the third on the life cycle of Leishmania (Kinetoplastida, Trypanosomatidae). The oral communications and posters were divided into five subsections, covering systematics at supraspecific, specific and subspecific levels, evolution, and life cycles of parasites with hosts in both aquatic and terrestrial environments. A wide range of topics was discussed, including recent developments in the fields of genetics and cellular and molecular biology, and computer-assisted numerical taxonomy.

Animals↗
PubMed1990

A technique for identification of cercariae of Schistosoma haematobium, S. curassoni, S. bovis and S. intercalatum.

The chaetotaxy of 84 samples or isolates of Schistosoma spp. from western or central Africa has been studied. Three indices were calculated for cercariae of each sample; their average value, the skewness and kurtosis of each indice was established. Each species (S. haematobium, S. curassoni, S. bovis and S. intercalatum) was discriminated with nine variables. The present work gives information to assess, specific diagnosis with simple calculations easily achieved on a small computer.

Animals↗
PubMed1990

[Timing niches of 3 species of Plasmodium coexisting in a rodent in Central Africa].

Freeze-thawing of blood infected with malaria parasites is a technique which brings about the destruction of all stages except the merozoites and makes possible investigations on the behaviour of these merozoites and the schizogonic rhythm of each species. Merozoites of Plasmodium y. yoelii remain in the blood during the 24 hrs. following inoculation; it is concluded that their penetration in the erythrocytes occurs gradually during this time. Synchronism is poor. Merozoites of P. vinckei petteri penetrate rapidly inside the erythrocytes independently of the time of inoculation. Infection is therefore synchronous and does not follow the circadian rhythm of the host. Penetration of merozoites of P. c. chabaudi is predominant at midnight when rodents are maintained with a normal circadian rhythm (light from 8 am to 8 pm) and predominant at noon when the rhythm of the host is inverted (light from 8 pm to 8 am). Infection is therefore synchronous and follows the host rhythm. The three species of plasmodia coexisting in Thamnomys rutilans from CAR show the same periodicity of 24 hrs. but, because of differences in the biology of the merozoites, they occupy three distinct niches. These notions have great practical implications in chronotherapy, as many data lead to the idea that merozoites are drug resistant.

Africa, Central↗
PubMed1989

Identification of Schistosoma haematobium, S. bovis and S. curassoni by multivariate analysis of cercarial papillae indices.

The disposition of cercarial papillae of 68 pre-identified Schistosoma species was established. All the cercariae originated from Africa and Madagascar and were either obtained from natural or experimental infections, and belonged to three species Schistosoma haematobium, S. bovis and S. curassoni. Discriminant analysis was based on nine characters: average values, skewness and kurtosis of three cercarial indices (AD, AL and U) for each sample or isolate. AD, AL correspond respectively to the relative distance between dorsal and lateral papillae. U corresponds to the total number of tail stem papillae. With the exception of two cases of the 68 (one of them corresponding to cercariae shed by a non-African experimentally infected snail), the method enabled discrimination of S. haematobium, S. bovis and S. curassoni.

Animals↗
PubMed1989

Species of the genus Elaphostrongylus parasite of Swedish cervidae. A description of E. alces n. sp.

A description of Elaphostrongylus alces n. sp., a parasite of moose (Alces alces L.), is given. The main features differing E. alces n. sp. from the other two investigated species are the bottle shaped oesophagus and the oval bursa, which is about 150 microns x 200 microns. E. rangiferi Mitskevith, 1960, a parasite of reindeer (Rangifer tarandus tarandus L.) and E. cervi Cameron, 1931, a parasite of red deer (Cervus elaphus L.) have both a club shaped or cylindrical oesophagus and a circular bursa. The bursa of E. rangiferi is about 160 microns in diameter, and the bursa of E. cervi is about 190 microns. Each species has been found only in its normal host.

Animals↗
PubMed1988

[New atractid nematode parasites of the chimpanzee and gorilla in Gabon].

Females of the genus Probstmayria, collected in feces of wild Chimpanzees and Gorillas, living in the Lope-Okanda reserve in Gabon, are described. The cephalic structures of P. gombensis File, 1976 from Chimpanzee and P. gabonensis n. sp. from Gorilla are similar to those of the other species of the genus. In contrast, the cephalic structures of P. inversa n. sp. from Chimpanzee and P. goodallae n. sp. from Gorilla are unusual; they have an inverse symmetry (one ventral lip and two latero-dorsal lips). The original characteristics of the genus Probstmayria are analysed.

Animals↗
PubMed1988

[Skrjabinelazia galliardi (Nematoda, Seuratoidea): morphologic complements and biological cycle].

Skrjabinelazia galliardi was previously known only from a description of the morphological characteristics of the female. Additional material being available, we were able to complete the morphological description and understand better the biology of the species. The male, the third stage larva and the fourth stage larva are described. Young females lay a very small number of third stage larvae, leading in a small scale to a reproduction of the atractide-type, that is a multiplication of the parasite directly inside the host. The old females are oviparous, but eggs contain a third stage infective larva. These eggs, after being ingested by field-crickets, hatch and without further development remain as larvae in the insect. The definitive entomophagous lizard host, which, in the field, has no opportunity to ingest the eggs, is infested by eating insects. So, the life history is intermediary between the cosmocercid like cycle (with three larval stages) and the spirurid-like cycle (with development of larval stages in an invertebrate).

Adaptation, Biological↗