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At least 19 recordsLinked to original sources

Complete nucleotide sequences of the mitochondrial genomes of two avian malaria protozoa, Plasmodium gallinaceum and Plasmodium juxtanucleare.

We analyzed mitochondrial genomes of two avian malaria protozoa, Plasmodium gallinaceum and Plasmodium juxtanucleare. Both mitochondrial genomes were estimated to be 6,002 and 6,014 bp in length, respectively, and to have the identical gene organization and contents to that of other Plasmodium species previously analyzed; three functional genes for cytochrome c oxidase subunit I, III, and cytochrome (cyt b), with following sets of discontinuous and scrambled 15 ribosomal subunit RNA (rRNA) genes. Similarities of the three protein-coding genes showed closer relationship within avian malaria protozoa rather than mammalian Plasmodium species. In addition, we showed the tandem repeated structure of each mitochondrial genome of both P. gallinaceum and P. juxtanucleare as well as previously found in mammalian Plasmodium species. This study revealed the complete sequences and structure of the mitochondrial genomes of avian malaria protozoa for the first time.

Animals↗

POTENTIATION OF ACTIVITY OF DIAPHENYLSULFONE AND PYRIMETHAMINE AGAINST PLASMODIUM GALLINACEUM AND PLASMODIUM CYNOMOLGI BASTIANELLII.

In view of the fact that diaphenylsulfone has been shown to have low schizontocidal activity against Plasmodium gallinaceum and to lead to resistance in strains of P. cynomolgi, investigations were undertaken into the joint action of diaphenylsulfone and pyrimethamine against P. gallinaceum in chicks and P. cynomolgi bastianellii in monkeys. These drugs were assayed separately and in various combinations. It was found that at certain dose levels combination of the two drugs led to potentiation of their plasmocidal activity. On the other hand, this synergistic effect was not noted with combinations containing lower dosages of either drug; with these, a simple additive effect occurred. The authors suggest that the two drugs probably act on the same metabolic pathway but that their points of attack may be different. They note also that there was a difference in the response of P. gallinaceum in chicks and of P. cynomolgi bastianellii in monkeys to the combined use of the two drugs.

Animals↗

3' UTR elements enhance expression of Pgs28, an ookinete protein of Plasmodium gallinaceum.

In Plasmodium parasites the fusion of gametes to form a fertilized zygote and morphogenesis into the motile ookinete are critical developmental stages in the parasite's complex life cycle. In analogous developmental stages of metazoan organisms 3' gene flanking regions are critical in the regulation of gene expression. To determine whether these mechanisms are conserved in the protozoan parasite we studied the 3' gene flanking elements necessary for the expression of Pgs28, the major surface protein of mature zygotes and ookinetes of the chicken malaria Plasmodium gallinaceum. The DNA sequence of the pgs28 3' gene flanking region contains 7 eukaryotic polyadenylation consensus signals (AATAAA/ATTAAA). An unusual 82% T-rich region is located 55 nucleotides upstream of the fifth polyadenylation signal (ATTAAA). The pgs28 mRNA terminates approximately 20 nucleotides from the polyadenylation signal in a poly (A) tail. To determine whether the T-rich region and polyadenylation signals were necessary for Pgs28 protein expression, sexual stage parasites were transfected with plasmids containing deletions of these elements utilizing firefly luciferase (LUC) and beta-glucuronidase (GUS) as markers of transient gene transfection. The parasites were allowed to develop in vitro to the ookinete stage and assayed for enzymatic activity. Cells transfected with plasmids containing deletions of the T-rich region or fifth eukaryotic polyadenylation consensus signal expressed 89 and 92%, less enzymatic activity respectively than those transfected with the full length pgs28 3' gene flanking region. The U-rich element and fifth eukaryotic polyadenylation consensus sequence within the pgs28 3' UTR are therefore necessary for Pgs28 protein expression.

3' Untranslated Regions↗

Penetration of the mosquito (Aedes aegypti) midgut wall by the ookinetes of Plasmodium gallinaceum.

We observed Plasmodium gallinaceum ookinetes in both intracellular and intercellular positions in the midgut epithelium of the mosquito Aedes aegypti. After epithelial cell invasion intracellular ookinetes lacked a parasitophorous vacuolar membrane and were surrounded solely by their own pellicle. Thus, the ookinete in the midgut epithelium of the mosquito differs from erythrocytic and hepatic stages in that the parasite in the vertebrate host is surrounded by a vacuole. The midgut epithelial cytoplasm around the apical end of invading ookinetes was replaced by fine granular material deprived of normal organelles. Membranous structure was observed within the fine granular area. Most ookinetes were seen intracellularly on the luminal side and intercellularly on the haemocoel side of the midgut epithelial cells. These observations suggest that the ookinete first enters into the midgut epithelial cell, then exists to the space between the epithelial cells and moves to the basal lamina where the ookinete develops to the oocyst.

Aedes↗

[Electron microscopic observation of the sporogonic stage of Plasmodium gallinaceum after five antimalarials].

Ultrastructural changes in Plasmodium gallinaceum oocysts and sporozoites were studies after 5 antimalarials (pyrimethamine, primaquine, artemisinine, 5-p-fluorobenzoxyl-primaquine citrate and nitroquine) were administered to Aedes albopictus. Obvious disfigurement, such as abnormal vacuoles of various sizes in the cytoplasma, thickened oocyst capsules and damaged sporozoite pellical membranes were found in many oocysts and sporozoites in the mosquitoes. When the grade of infection of sporozoites in the salivary glands of the 5 different groups of mosquitoes were compared with the control, the rank test (Hc = 271) showed a very significant variance (P less than 0.01).

Aedes↗

Infectivity of Plasmodium gallinaceum sporozoites from oocysts.

Infectivity of Plasmodium gallinaceum (Brumpt) sporozoites isolated from midguts and salivary glands of experimentally infected Aedes fluviatilis (Lutz) was studied. The 2 populations were compared at 7, 8, and 9 days postisolation from mosquitoes, which were maintained at 27 C +/- 1 C and approximately 75% relative humidity. Infectivity of the parasites was evaluated by the length of the prepatent period of the infection in 2-week-old chicks inoculated intramuscularly. Infection was caused by 7-day-old sporozoites from salivary glands, but not from midguts. Older sporozoites induced infection in all the inoculated chicks. The results suggested a somewhat higher infectivity of the 8- and 9-day salivary-gland parasites than of the oocyst sporozoites. However, unlike sporozoites from mammalian malaria, oocyst sporozoites from avian malaria were highly infective at this age.

Aedes↗