Differences in the characteristics of the culture conditions can influence the multiplication rate of Plasmodium falciparum. The Petri dish method is one of the most popular methods of cultivating this parasite. In many previous studies, ideal culture conditions of the Petri dish method were achieved by using erythrocytes collected from blood that had been stored for at least 2 weeks, with daily changes of the medium. In the present study, we studied the multiplication rate of P. falciparum in cultures containing erythrocytes of various ages together with changing the medium at various intervals of time. Our results strongly suggest that the rate of in vitro multiplication of P. falciparum was higher in freshly collected erythrocytes than in aged erythrocytes regardless of the anticoagulant and that when the parasitemia is lower than 8% with a hematocrit of 5%, the medium change interval can be as long as 48 hr without a great reduction in the rate of multiplication.
Animals ; Blood Specimen Collection ; Cell Aging ; Culture Media ; Erythrocytes/*parasitology ; Plasmodium falciparum/*growth & development ; Time Factors

Artemisinin-based combination therapy (ACT) is currently promoted as a strategy for treating both uncomplicated and severe falciparum malaria, targeting asexual blood-stage Plasmodium falciparum parasites. However, the effect of ACT on sexual-stage parasites remains controversial. To determine the clearance of sexual-stage P. falciparum parasites from 342 uncomplicated, and 217 severe, adult malaria cases, we reviewed and followed peripheral blood sexualstage parasites for 4 wk after starting ACT. All patients presented with both asexual and sexual stage parasites on admission, and were treated with artesunate-mefloquine as the standard regimen. The results showed that all patients were asymptomatic and negative for asexual forms before discharge from hospital. The percentages of uncomplicated malaria patients positive for gametocytes on days 3, 7, 14, 21, and 28 were 41.5, 13.1, 3.8, 2.0, and 2.0%, while the percentages of gametocyte positive severe malaria patients on days 3, 7, 14, 21, and 28 were 33.6, 8.2, 2.7, 0.9, and 0.9%, respectively. Although all patients were negative for asexual parasites by day 7 after completion of the artesunate-mefloquine course, gametocytemia persisted in some patients. Thus, a gametocytocidal drug, e.g., primaquine, may be useful in combination with an artesunate-mefloquine regimen to clear gametocytes, so blocking transmission more effectively than artesunate alone, in malaria transmission areas.
Adolescent ; Adult ; Animals ; Antimalarials/*pharmacology/therapeutic use ; Artemisinins/*pharmacology/therapeutic use ; Drug Evaluation ; Drug Therapy, Combination ; Female ; Follow-Up Studies ; Germ Cells/*drug effects/growth & development ; Humans ; Malaria, Falciparum/*drug therapy/parasitology ; Male ; Mefloquine/*pharmacology/therapeutic use ; Plasmodium falciparum/*drug effects/growth & development ; Severity of Illness Index ; Thailand ; Treatment Outcome

The onset, severity, and ultimate outcome of malaria infection are influenced by parasite-expressed virulence factors and individual host responses to these determinants. In both humans and mice, liver injury is involved after parasite entry, which persists until the erythrocyte stage after infection with the fatal strain Plasmodium falciparum (Pf). Hepatocyte growth factor (HGF) has strong anti-apoptotic effects in various kinds of cells, and also has diverse metabolic functions. In this work, Pf-subtilisin-like protease 2 (Pf-Sub2) 5'untranslated region (UTR) was analyzed and its transcriptional activity was estimated by luciferase expression. Fourteen TATA boxes were observed but only one Oct-1 and c-Myb were done. In addition, host HGF interaction with Pf-Sub2 was evaluated by co-transfection of HGF- and Pf-Sub2-cloned vector. Interestingly, -1,422/+12 UTR exhibited the strongest luciferase activity but -329 to +12 UTR did not exhibit luciferase activity. Moreover, as compared with the control of unexpressed HGF, the HGF protein suppressed luciferase expression driven by the 5'untranslated region of the Pf-Sub2 promoter. Taken together, it is suggested that HGF controls and interacts with the promoter region of the Pf-Sub2 gene.
*5' Untranslated Regions ; Artificial Gene Fusion ; Cell Line ; Genes, Reporter ; Hepatocyte Growth Factor/*metabolism ; Hepatocytes/parasitology ; *Host-Parasite Interactions ; Humans ; Luciferases/genetics/metabolism ; Plasmodium falciparum/*pathogenicity ; Protein Binding ; Subtilisins ; *Transcription, Genetic

Plasmodium falciparum (P. falciparum) is responsible for the majority of life-threatening cases of human malaria, causing 1.5-2.7 million annual deaths. The global emergence of drug-resistant malaria parasites necessitates identification and characterization of novel drug targets and their potential inhibitors. We identified the carbonic anhydrase (CA) genes in P. falciparum. The pfCA gene encodes anα-carbonic anhydrase, a Zn(2+)-metalloenzme, possessing catalytic properties distinct from that of the human host CA enzyme. The amino acid sequence of the pfCA enzyme is different from the analogous protozoan and human enzymes. A library of aromatic/heterocyclic sulfonamides possessing a large diversity of scaffolds were found to be very good inhibitors for the malarial enzyme at moderate-low micromolar and submicromolar inhibitions. The structure of the groups substituting the aromatic-ureido- or aromatic-azomethine fragment of the molecule and the length of the parent sulfonamide were critical parameters for the inhibitory properties of the sulfonamides. One derivative, that is, 4- (3, 4-dichlorophenylureido)thioureido-benzenesulfonamide (compound 10) was the most effective in vitro Plasmodium falciparum CA inhibitor, and was also the most effective antimalarial compound on the in vitro P. falciparum growth inhibition. The compound 10 was also effective in vivo antimalarial agent in mice infected with Plasmodium berghei, an animal model of drug testing for human malaria infection. It is therefore concluded that the sulphonamide inhibitors targeting the parasite CA may have potential for the development of novel therapies against human malaria.
Animals ; Antimalarials ; pharmacology ; therapeutic use ; Carbonic Anhydrase Inhibitors ; pharmacology ; therapeutic use ; Carbonic Anhydrases ; chemistry ; genetics ; metabolism ; Catalysis ; Genome, Protozoan ; Genomics ; Humans ; Life Cycle Stages ; Malaria, Falciparum ; drug therapy ; parasitology ; Parasites ; drug effects ; enzymology ; Plasmodium falciparum ; drug effects ; enzymology ; genetics ; growth & development ; Protein Conformation ; Sulfonamides ; pharmacology ; therapeutic use