Spinning disk confocal microscopy of live, intraerythrocytic malarial parasites. 1. Quantification of hemozoin development for drug sensitive versus resistant malaria

We have customized a Nipkow spinning disk confocal microscope (SDCM) to acquire three-dimensional (3D) versus time data for live, intraerythrocytic malarial parasites. Since live parasites wiggle within red blood cells, conventional laser scanning confocal microscopy produces blurred 3D images after reconstruction of z stack data. In contrast, since SDCM data sets at high x, y, and z resolution can be acquired in hundreds of milliseconds, key aspects of live parasite cellular biochemistry can be much better resolved on physiologically meaningful times scales. In this paper, we present the first 3D DIC transmittance "z stack" images of live malarial parasites and use those to quantify hemozoin (Hz) produced within the living parasite digestive vacuole, under physiologic conditions. Using live synchronized cultures and voxel analysis of sharpened DIC z stacks, we present the first quantitative in vivo analysis of the rate of Hz growth for chloroquine sensitive (CQS) versus resistant (CQR) malarial parasites. We present data for laboratory strains, as well as pfcrt transfectants expressing a CQR conferring mutant pfcrt gene. We also analyze the rate of Hz growth in the presence and absence of physiologically relevant doses of chloroquine (CQ) and verapamil (VPL) and thereby present the first in vivo quantification of key predictions from the well-known Fitch hypothesis for CQ pharmacology. In the following paper [Gligorijevic, B., et al. (2006) Biochemistry 45, pp 12411-12423], we acquire fluorescent images of live parasite DV via SDCM and use those to quantify DV volume for CQS versus CQR parasites.