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Biomedical subjects

F Miltgen

Publications and source records attributed to F Miltgen.

At least 73 records · Page 4Linked to original sources
PubMedDate not supplied

Activity of dihydrofolate reductase inhibitors on the hepatic stages of Plasmodium yoelii yoelii in vitro.

The effects of the dihydrofolate reductase inhibitors proguanil and chlorproguanil, their active metabolites cycloguanil and chlorcycloguanil, and pyrimethamine, against the hepatic stages of Plasmodium yoelii yoellii were investigated in cultured BALB/c mouse hepatocytes. Proguanil was inactive at concentrations of 10(-8) M, whereas the other compounds were fully active at this and lower concentrations. Chlorcycloguanil was the most active compound and almost completely inhibited schizont development in concentrations as low as 10(-12) M.

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PubMedDate not supplied

Cultivation of the liver forms of Plasmodium vivax in human hepatocytes.

The blood schizogonic cycle of human malaria parasites has thus far been the most exhaustively studied phase of parasite development. However, before entering red blood cells (RBCs), the parasite undergoes its first multiplication not in blood, but in hepatic cells. These hepatic stages were the last to be discovered and only a few studies have been performed in humans and other primates. Despite recent advances, in vivo studies have limitations and other approaches such as cultures of these liver forms may be necessary to investigate their chemosensitivity and their biochemical or immunological properties. Recently, sporozoites of species of rodent malaria have been made to infect cultured cell lines or primary hepatocyte cultures. We report here that the complete cycle of the human malaria parasite Plasmodium vivax can be obtained in primary cultures of human hepatocytes up to release of merozoites able to penetrate RBCs.

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PubMedDate not supplied

Ultrastructural observations on the merocyst and gametocytes of Hepatocystis spp. from Malaysian squirrels.

An immature merocyst of Hepatocystis malayensis and gametocytes of H. brayi were studied with the electron microscope. The merocyst consisted of a highly complex cytoplasmic reticulum ramifying through an amorphous matrix: the entire complex was enclosed by a simple unit membrane. The host cell was apparently destroyed completely during growth of the cyst. Immature gametocytes were highly amoeboid and showed extensive vacuolisation or attenuation of the cytoplasm. The nucleus contained one or two prominent nucleoli. Mature gametocytes had compact cytoplasm and contained pyriform osmiophilic bodies which were believed to function in the release of the parasites from the host cells. Macrogametocytes were distinguished from microgametocytes by cytoplasmic differences in numbers of ribosomes, and cristate mitochondria and in the extent of development of the smooth endoplasmic reticulum. The compact nuclei of the macrogametocytes had inconspicuous DNA but prominent nucleoli whereas those of the microgametocytes were irregular and showed a central aggregate of DNA. In microgametogenesis karyokinesis of the parent nucleus was delayed until axoneme formation was complete. Then the nuclear buds were extruded into emerging microgametes. At fertilisation the plasmalemmas of the two gametes fused and the single axoneme and nucleus of the microgamete moved into the cytoplasm of the macrogamete.

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PubMedDate not supplied

[Hepatocystis brosseti n. sp. Haemproteidae, parasite of Epomops franqueti, Pteropinae, in Gabon].

Epomops franqueti (Pteriopinae) trapped around Makokou (Gabon) are frequently infected with Hepatocystis brosseti n. sp. Blood smears and tissue sections were made; all schizonts were found in the liver except a single one in the spleen. In liver, near maturity the schizonts are extracellular, convoluted, medium sized (250 mu) and filled with abundant colloidal substance.

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[Dionisia bunoi n. g. n. sp., Haemoproteidae parasite of the microchiropteran bat Hipposideros cyclops in Gabon (author's transl)].

Dionisia bunoi ng. g., n. sp. is characterized by:--a) sexual dimorphism of gametocytes, macrogametocyte of the falciparum type, microgametocyte of the type malariae:--b) schizonts developing in the lumen of liver blood vessels inside a greatly hypertrophied host cell; their size remains moderate and their cytoplasm is not intensely basophilic as is usually in the young stages of Haemosporidia of Mammals. The genus has morphological characters in common with each of the 4 other genera of Haemoproteidae of Mammals. The phyletic hypothesis concerning the morphology of gametocytes and schizonts suggests that Bioccala and Dionisia are primitive.

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[Study of gametocytes from the Plasmodium "vivax" group: morphology, development in Anopheles and infectivity of Plasmodium yoelii microgametocytes].

The study of the gametocytes of Plasmodium yoelii enabled the differentiation of 4 morphological types: O, I, II and III (in a chronological order) and amongst each of these types the differentiation of healthy and altered gametocytes. These morphological data represent a tool for investigations on the biology of the gametocytes of the "vivax" group. Preliminary experiments bring informations on the evolution of gametocytes and the mechanisms of their infectivity. 1--In experimentaly infected white mice gametocytes of P.y. nigeriensis are infective up to the 3rd-4th day, those of P. y. yoelii until the 5th-6th days. These periods can be shorter when the infection is very virulent or longer when chronical. 2--The drop in infectivity coincides with the increase in number of the altered gametocytes. 3--The loss of infectivity is connected with the condition of the blood: when parasitaemiae are high, it becomes rapidly unsuitable to a normal evolution of the gametocytes: thus, non infective gametocytes acquire a good infectivity in less than two hours when transfered to a clean mouse. 4--The gametocytic composition of the blood taken up by the Anopheles in the capillaries can be very different from that taken at the tail of a Rodent. In the young parasitaemiae, when the Rodents are most infective to the Mosquitoes, there is a considerable enrichment in gametocytes O-I of the blood ingested by the Anopheles as compared to that taken from the Rodents by the usual techniques. This phenomenon could perhaps be explained by the larger size of gametocytes O and I and their retention in the capillaries of the host. 5--The strong infectivity of gametocytes O and I is confirmed by the fact that no infection develops in the Mosquitoes when no such gametocytes are present in the ingested blood. 6--The ageeing of gametocytes appears to be very rapid for gametocytes arising from exo-erythrocytic schizontes reach stage II, 29 hours and stage III, 35 hours, after the rupture of the very first schizonts.

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[Trypanosoma (Megatrypanum) lizae n. sp.: a trypanosome with giant forms from the Michrochiroptera Hipposideros cyclops, in Gabon (author's transl)].

Trypanosoma (Megatrypanum) lizae n. sp.: trypanosome with giant forms reaching a length of 1400 micrometers from the Microchiroptera Hipposideros cyclops in Gabon. Because of the peculiar morphology of giant forms and the characteristics of small individuals it is placed in a new species within the subgenus Megatrypanum.

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PubMedDate not supplied

[Morphology and infectivity of gametocytes of Plasmodium inui].

The authors report biomorphological changes of Plasmodium inui gametocytes during the natural infection of spleenless Macaca fascicularis. The infection was controlled up to the 42th day by smears produced by pricks into their ears (P.O.) and on blood taken at the same time by A. stephensi (P.M.). The first oocystes appeared on the 8th day after the infection in mosquitoes fed on the monkey parasitised in the eight day after splenectomy, as gametocytaemia was not detectable yet in the P.O. smears. The infectivity of gametocytes is highest on the 13rd day for a 152/10(4) parasitaemia. The first sporozoites appeared on the 18th day at 25 degrees C after the infecting meal. The sporozoites were infecting for a second monkey. Four morphological types (O, I, II and III) gametocytes were identified. They corresponded to the same types previously described in rodent Plasmodium. The maximum of infectivity coincided with a sudden increase in mosquitoe macrogametocytaemia; on the other hand the infectivity was very weak during the following peek of macrogametocytaemia which corresponded however to the maximum of parasitaemia (1 318/10(4) 18 days after splenectomy). When infectivity was important, there was a greater number of type O and I gametocytes in P.M. than in P.O. Eventually, the behaviour of P. inui gametocytes is, for the mainly, almost the same as that of rodent Plasmodium. However, it is to be noted that the identification of the 4 morphological types in P. inui is easier in macrogametocytes than in microgametocytes. The reverse had been observed in rodent Plasmodium.

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PubMedDate not supplied

[Different types of gametocytes in mammal's Haemosporidia. Correlations with the morphology of the tissue schizonts. Hypothesis on the evolution of the group (author's transl)].

The Haemosporidia of Mammals are classified in 3 groups according to the morphology of the gametocytes: 1) group "vivax" with Hepatocystis and several species of Plasmodium; 2) group "malariae" with Nycteria and a second group of Plasmodium; 3) group "falciparum" with only Plasmodium. In each group there is a correlation between the morphology of the gametocytes and that of the exo-erythrocytic schizonts. Through discussing the host-range and comparing the life cycles of Haemosporidia in Birds, Reptiles and Mammals, we suggest a hypothesis of the polyphyletism of Plasmodium of Mammals.

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