Trophozoite stage

Malaria is a worsening problem worldwide. More than 110 million people suffer from infection every year and up to 2 million of these die. A growing number of countries are now affected by drug-resistant strains of the parasites. The introduction of an iron chelator to control such infection is a novel approach, and as chelation is particularly critical at the late trophozoite stage, it may prove possible to limit treatment to relatively short time periods. 

The malarial parasite, Plasmodium falciparum, was grown in red blood cells to the late trophozoite stage. Cells isolated by centrifugation were lysed with saponin, and the intact parasites were resuspended in 10 mM Hepes-KOH buffer (pH 8.0) at a dilution of 1 3. 

Immunize BALB/c mice intraperitoneally at 3-wk intervals with the erythrocyte membranes isolated from approx 1.5 x 107 mouse erythrocytes infected predominantly with the trophozoite stage of P. berghei. 

Although PS accounts for less than 5% of Plasmodium lipids, it is a key intermediate in the synthesis of PE, which serves as a precursor to PC (see above). PS is synthesized by a condensation of serine with CDP-DAG catalyzed by PS synthase (PSS). Initially, PSS was characterized biochemically in P. knowlesi and later P. falciparum (Elabbadi and Vial, personal communication). Two putative genes that possibly encode PSS have been identified in the P. falciparum genome base and a recombinant protein has been made. In P. falciparum, the putative PSS gene is transcribed during the ring and trophozoite stages. PS decarboxylation via PS decarboxylase (PSD) was first demonstrated in P. knowlesi-miected red cells where it was found that radiolabeled serine was incorporated into Etn (Elabbadi et ah, 1997). 

Bozdech, Z., Zhu, J., Joachimiak, M. P., Cohen, F. E., Pulliam, B., and DeRisi, J. L., 2003, Expression profiling of the schizont and trophozoite stages of Plasmodium falciparum with a long-oligonucleotide microarray. Genome Biol 4 R9. 

To establish the equivalence of the j3-hematin from the two prqiarations in equations 3 and 4 with prior results we have characterized these compounds by elemental analysis, infrared spectroscopy, Raman spectroscopy, magnetic susceptibility. X-ray powder diffraction, and diffuse reflectance specd oscopy. The analytical results agree within experimental error with those reported by Slayter et al. (C, 64.7 H, 5.0 N, 8.7%) for 3-hematin prepared by the thermal dehydration reaction in equation 2 (IS). These results in turn are similar to those obtained for malaria pigment isolated from P. falciparum in die late trophozoite stage IS). 

---