COMPARATIVE-STUDY OF KINETOPLAST DNA IN CULTURE, BLOOD AND INTRACELLULAR FORMS OF TRYPANOSOMA-CRUZI

A comparative study has been made on the kinetoplast DNA (kDNA) form I in culture epimastigote, blood trypomastigote and intracellular amastigote stages of Trypanosoma cruzi. The basic properties of the kDNA in all 3 forms were identical. Thus the DNA was in the form of networks of density 1.698-9 g/cm3 and with sedimentation coefficients (S20,w) of ∼ 5500, the networks being composed of large complexes of minicircular and apparently linear molecules, the former having contour lengths of 0.45 μm. Several differences were noted. The ultrastructural arrangement of the kDNA in the kinetoplast of the blood stage consisted of three to four double rows of DNA as compared to one double layered row in the other two stages. There was proportionately more kDNA in the blood stages, suggesting that, since the networks have apparently the same size (see above), more than one is present. DNA loops situated at the periphery of the kDNA networks were observed in higher proportion in blood and intracellular forms. Dimeric and oligomeric circles were present in the kDNA of the blood and intracellular stages in much greater proportion than in culture epimastigote stages. Few large circular molecules, heterogeneous in size, were also observed in intracellular blood stages. There were some differences, mainly quantitative, in the gel electrophoresis patterns after endonuclease digestion. © 1978 Masson, Paris.